Tokyo plans to retrofit 1964 Olympics stadiums for the 2020 games

Tokyo was chosen as the host of the 2020 Olympics this weekend.

To host the 2020 Olympics, Japan offered a $5 billion bid -- surprisingly low, compared to the money spent by other recent host cities.

At the heart of the city's proposal was a plan to retrofit three major venues originally built for the 1964 Summer Games amid Japan's ongoing recession.

Tokyo's bid is a streamlined, more tightly budgeted version of what Olympics host cities usually choose. The stadiums will get dramatic makeovers with contemporary perks, including a retractable roof for the main stadium.

Architect Zaha Hadid will use the original bones of the Nippon Budokan and the Tokyo Metropolitan Gymnasium -- two other 1964 games structures -- to create structures for the 2020 Olympics. The city already has extensive transit systems in place and will not have to invest much in it to prepare for larger crowds.

There will still be dozens of new structures built, but they will fill in spaces in downtown Tokyo to reduce transit times and energy costs. A compact Olympic Village will be built on Tokyo Harbor and will be converted into housing after the games.