Roosevelt Island

From the National Park Service:
"In the 1930s landscape architects transformed Mason’s Island from neglected, overgrown farmland into Theodore Roosevelt Island, a memorial to America’s 26th president. They conceived a “real forest” designed to mimic the natural forest that once covered the island. Today miles of trails through wooded uplands and swampy bottomlands honor the legacy of a great outdoorsman and conservationist."

This island sits in the Potomac River, just west of the city center.
Accesible only from the northbound lanes of the George Washington Memorial Parkway or via pedestrian bridge. In the middle of the island there is a bronze statue of Teddy Roosevelt and 4 granite tablets inscribed with his philosophies.