It's actually a moat. The purpose is to simulate a toilet bowl. It will be "active" for about 80% of the Commanders related activities up to, and including, game day festivities.
It's Danish designed?
LOL nothing more American than the D.C. team in a Danish soccer stadium. I guess it is for a lot of other events like the wooden shoe making world championships.
NFL Stadiums do not last as long anymore due to the Teams don't share income made at the Stadium itself. So, it's always a "Keeping up with the Jones" (literally in this case)
The crappy thing about it is the tax payers pay for hundreds of millions of dollars of the cost, yet get nothing except incredibly expensive PSL and high ticket charges in return.