Workers are building the $810-million Olympic Stadium with 80,000 seats and a partial roof. But in 2012, soon after officials of London Games hang the final medals around the necks of the winning athletes, crews will move back in to shrink the venue down to its "legacy mode," with only 25,000 seats and no roof. Consequently, from the start of design, a "here today, two-thirds gone tomorrow" attitude dominated the team's thinking. The project marks “a new era of Olympic stadium design...demonstrating how a successful event can be blended with the long term needs of a community,” claims Rod Sheard,
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.