Columbia River, U.S.A.

Forming much of the border between the states of Oregon and Washington, the Columbia River is the largest North American river, by volume, that flows into the Pacific Ocean. Salmon hatch in its waters, migrate downstream to the Pacific Ocean, and return against the current to breed. The fish are threatened by efforts to dam the river for electricity generation. Rising temperatures will add to their troubles.

Floating Stadium

Made entirely of steel, the floating platform on Marina Bay measures 120 metres long and 83 metres wide, which is 5% larger than the soccer field at the National Stadium. The platform can bear up to 1,070 tonnes, equivalent to the total weight of 9,000 people, 200 tonnes of stage props and three 30-tonne military vehicles. The gallery at the stadium has a seating capacity of 30,000 people.

But do they have boats cruising around during the games to catch all those balls that were kicked outside the field?