Seventy-three days before the beginning of the London Olympics, the Olympian construction race — which began seven years ago in the United Kingdom — is reaching the tape. The first large scale public visit to the 225 hectare Queen Elizabeth Olympic Park took place last week, and three weeks ago London Mayor Boris Johnson opened the Orbit viewing tower-cum-folly, which stands next to the completed Stadium and a stone's throw from Zaha Hadid Architects' Aquatics Centre. From the viewing point at its summit, 22 metres taller than New York City's Statue of Liberty and above curlicues of red painted steel, Canary Wharf and the City of London look minute. Here, in East London, from this mix of sporting icons and regenerated swathes of territory, is emerging a "new piece of city", explained Ricky Burdett at The architecture of the Olympics, a sell-out talk at the London School of Economics (LSE) last 15 May. Burdett is Professor of Urban Studies, Director of LSE Cities and was from 2006-10 Chief Advisor on Architecture and Urbanism to the Olympic Delivery Authority (ODA), and thus described the goal of the Olympics project.

The event was one of the first opportunities, explained chair and Director of Tate Sir Nicholas Serota, to reflect on issues this massive renewal project provoked, and the lessons learned. Serota has played the role of design champion, along with Burdett and others at the ODA for over 10 years. There, they have consistently pushed the longer term, evolutionary imperative for this site of "sustainable games", whose development has cost 11,65 billion euros. The praxis of the project stems from the choice of London for the Games, and with speakers from three practices, the evolution of three key sports venues was given a lot of air time at the talk. The Basketball Arena, designed by Wilkinson Eyre, will be dismantled and used elsewhere after the Games. The Aquatics Centre, for which Zaha Hadid Architects was the first practice to be appointed in 2004 — with Burdett on the jury —, will act as the gateway to the Park during and after the Games. Michael Hopkins & Partners' Velodrome will, post-Games, be surrounded by a new VeloPark serving the local community. The Centre will make up for the lack of good quality Olympic-sized swimming pool in London, and both should help overcome the paucity of local public buildings of any calibre.

Ruled by the International Olympic Committee's (IOC) seven year timescale for realisation, the plan for the Olympic facilities originally involved creating venues across London, with a focus on Stratford, in the Lower Lea Valley. However, behind the emphasis on venues suggested by LSE's event title is a much larger story, about a long awaited goal to respond to urban growth by reinventing the area and boosting its jobs, building "human infrastructure representing the waves of immigration from all over the world to 360 degrees around the site", as Burdett put it. "London (planning) policy has for 20-30 years tried to shift east/north-eastwards to areas where there is a lot of land, while West London is less deprived." East London is an area that "really needed the money", as former London Mayor Ken Livingstone put it at the time of the IOC bid, with some of the worst socially deprived urban environments in the whole of the UK, in the boroughs of Tower Hamlets, Newham and Hackney.

The site's disconnection was also a handicap. Ricky Burdett showed the single road cutting across the site depicted in the 2005 A-Z London map. Today, the area is laced across with new bridges, paths and a multi-modal transport infrastructure backbone. The brownfield site was "for hundreds of years the backwater of London", the former location of large amounts of industry. But the area is also romantically evocative, with a series of green, connected landscapes with waterways linking the River Thames to the south, more rural counties north of London and up to the north of England.

According to Burdett, seven years is not a lot of time to build a major piece of city — and the East London's development will continue after the Games, on a 20-25 year timeframe. Responsibility for the district's legacy plans has been assumed by the OPLC, a body founded a few years ago that was in April 2012 renamed the London Legacy Development Corporation (LDDC). It takes the baton from the ODA. The American planner Andy Altman, Chief Executive since 2009, is steering the transmutation of the 120 hectare site into "a vibrant and mixed community", rebalancing London's growth. At the LSE event, Altman was at pains to point out that this was "a very conscious building of the city", not "leaving (it) all to the market, selling off parcels". It is being "nurtured with a 100 year view", he explained, in the "tradition in London of the great estates still existing and much loved today: Mayfair, Chelsea, Marylebone, Notting Hill and Pimlico."

The identity of the future district will start to coalesce after the Games with the removal of the temporary venues, so that the land they occupy can be converted into new neighbourhood residential, sports and leisure facilities, a shrewd adaptive strategy avoiding "white elephants". The departing Basketball arena will make way for Chobham Manor, the first residential development; the water polo arena space becomes a mixed outdoor sports area and part of Stratford Waterfront with restaurants, bars and cafes; the riverbank platform for hockey and ParaOlympic football will become a space for events and then housing, while the pools at Eton Manor to the northeast will become the Lee Valley Hockey and Tennis Centre.

Jim Eyre, Director of Wilkinson Eyre, likened the white PVC fabric covered temporary Basketball arena to a take-away. He would have preferred to do a geodesic dome, but in the end, their choice of design for the vast 300,00 square metre volume in lightweight steel — with night lighting by interactive designers United Visual Artists — is two-thirds recyclable, and could be "divided up and used as small halls for schools", or maybe "it goes off to Rio" for the Olympics in 2016. The Rio organizers have already spent a lot of time in London looking at things and, for them and the IOC, it must surely become a reality that inventive, reconfigurable architecture helps increase sharing of venues between countries.

Presented by Senior Partner at Hopkins Architects Mike Taylor, the design of the permanent Velodrome, housing the UK's most successful sport, triumphed over the "no, you can't do that attitude" of the clients. Fortunately world champion cyclist Chris Hoy sat on the jury. With very few velodromes in the world, Hopkins Architects wanted to "rewrite the script", outdo the "beautiful cable net structure of the Munich velodrome in 1972", and have architecture and engineering striving for the efficiency of a bicycle, an update on the heritage of Brunel. Unlike the 1948 Games in London, when the velodrome was outdoors —"the Pringle", as it is dubbed —, the 2012 construction needed to achieve optimum "breathability", acoustics and atmosphere with the geometry of the track bringing the public (who like it breathable) as close as possible to the cyclists (who like it hot). For Taylor, the Olympic project overall was "a model showing how you could do more with less."

Like the other two architectural practices, Zaha Hadid Architects (ZHA) had never built a sports venue before. This was something important for the competition judges early on, Sir Nicholas Serota pointed out, based on a "faith in challenging architects with a capacity to respond with inventiveness, vindicated in the result". For Jim Heverin, Associate Director at ZHA, the responses on the "very difficult east End site" lends the results authenticity as a London design statement. The Aquatics Centre went through many iterations, becoming more compact (Beijing's Water Cube was far larger) but retaining the core design. "We tried to create a pavilion in the park, very fluid, open and transparent, encouraging people to come in and use, observe or test out its sculptural diving boards. The landscape is as close as possible, so when you are swimming it feels like you are close to the park. The language fits into the wider park language".

The pledge to put East London on the map by creating a new mixed neighbourhood, responding to "an enormous need for new housing", definitely helped London win the bid. This attention to the long term needs of the city goes against the grain of many Olympics, for while Munich in 1972 and Barcelona in 1992 "left really good models behind", said Ricky Burdett, Athens' approach proved "a waste of infrastructure and investment" in the long term. As for Beijing, as spectacular as Herzog & de Meuron's Bird's Nest was, "no one can use it afterwards." But if not through the televisual Bird's Nest, China did, however, make advances, according to the United Nations. The UN's Environment Programme report of 2009 conceded Beijng a big green tick for creating an eco-friendly Games with a number of venues enabling a green legacy for further planning.

Although Andy Altman did not present the LDDC's new sustainability guide, the London Olympic project's sustainability was defined as an adaptable planning strategy: with recyclable and eco-sound venues, there is scope to make changes very soon after the Games to bring the rest of the new district into being. But what kind of identity will the 21st century estate have? Both Altman and Burdett conjured up a vision of a new 21st century garden city of a kind that would "bring nature into the city", which hopefully means avoiding the suburbanism of the 20th century garden city. Altman is moved by the idea of "great public spaces, and the city fills in around them", citing the past, when even London's South Bank "was considered an edge of the city".

As for the fit between residents, how do you create a mixed community? Porosity helps: the context may have only had one road across it at the outset of the project: now it is far more connected by bridges running across the site. There will be a certain test site atmosphere. The enabling of community resources will be vital. The statistics for the clusters of mixed residential areas showed a commitment to affordable housing, maybe not enough since so many people are priced out of housing in London. The first complex to be built, will adapt the Athletes' Village into what is to be known as the East Village. The building will feature 2818 new homes, with a mix with 50% affordable tenures and shared equity. Across the masterplan, 35% of the 8000 zero carbon homes will be affordable, with a diversity in housing types, with the high density Chobham Manor by the Park, a residential development to be completed by 2015 to "set the tone". Chobham Manor will feature up to 70% terraced family houses, vital in relation to the demographics, so long as enough alternative types coexist.

At the event, no one framed a question about this, but the issue of avoiding the worst aspects of suburbia — or indeed enclavism — is important. There have been many of discussions by those involved about the identity of the residential areas, and while that was not hinted at, Andy Altman was keen to state: "this isn't a gated community." Alongside physical integration — building on the excellent transport infrastructure — would be social integration, he said. Quite how many people will regularly visit from other parts of London, how well the different communities will mix, is open to conjecture at this point. But alongside the forging of community centres, or "places of exchange" as architect and advisor Stephen Witherford put it, Altman has underway a huge array of opportunities for "temporary enterprise" uses, events and activities. This "soft" or micro- planning appears to suggest that the site will be a very lively place with potentially something for everyone. Spatially, can it work in legacy mode simultaneously as a visitor attraction and a place to live? Central London already does but in many ways, of course, space is contested.

As for the economic and social sustainability of the new district after the Games, Altman felt that the mechanism of the LLDC, a corporation that owned the land it was nurturing, gave it a huge asset in delivering on its vision. "It doesn't just happen with the free market, organically." Ironically, though, it was the free market in the form of LendLease, London & Continental Railways and Westfield who were the early instigators of Westfield Stratford City, including its new 175,00 square metre shopping mall (one of the largest in Europe) and International Station, where anyone travelling to the site by train will first arrive.

LSE's The architecture of the Olympics event was about the legacy district and three of its Olympics venues, and did not trigger discussions about the identity of what is already emerging there as an intense mix of work, retail, leisure and residential units. Walking back from the Olympic Park to the Stratford rail links, it is hard to see any attempt by the architects of Stratford City to create buildings complementing the Park itself, so the fit between the two masterplans will hopefully be discussed in the autumn, when a further event will be staged at LSE Cities on this aspect of the project.

The resolutely top-down nature of the Olympics project is clear, but the soft planning of the adaptive stages of the scheme, incubating new community facilities, should enable the kind of rhizomatic, grassroots growth to really embed the "living legacy" piece of city into London's vast and evolving territory and popular imagination. Ricky Burdett is optimistic: "It's a very resilient fabric, and over time you'll have a cocktail. It'll sustain things that we don't know about because they become more complex — rather than more simplistic — over time".

Lucy Bullivant's new book Masterplanning Futures is published by Routledge on 10 July 2012.