In the 80's when I was running around DC we used to swim in the many fountains around the city. Nothing more fun than leaving Hawk'n Dove or Bullfeathers, the Tombs, 9:30 club or BlackCat at 1:30am and taking a dip with new-found, inebriated friends in the Taft Memorial, G'town Harbor, or any number of others. I suppose your kids are too young for that, and you are now at the other end of the spectrum.

Seriously - many of the new condo buildings have rooftop pools - so you might look for AirBnB-type listings with pools.