If you're into urban hiking and exploration, this is your spot. It's just across the river from Georgetown and DC, and totally worth the walk/drive. We always joke that this is where they keep Teddy Roosevelt, which is kind of true - on the middle of the island, there is a huge monument to the big man himself. I've picnicked here, I've hiked through the marshlands here, and it feels like a staycation every time.
Theodore Roosevelt Island, Washington, DC, USA