The Floating Stadium

Known as The Float at Marina Bay (or Marina Bay Floating Platform), this floating stadium is the world's largest floating stage. It is located on the waters of the Marina Reservoir, in Marina Bay, Singapore.

Made entirely of steel, the floating platform measures 120 metres long and 83 metres wide. It 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.
The stage took 13 months to build, and by April 2007, the platform and seating gallery were completed.

I think it's a great idea, but the grandstands seem to be quite far.