This place is a local favorite. It's just a giant field that ends at the Potomac River (go a little further north on the parkway or bike trail for views of the monuments). It's great for riding bikes (the trail stretches from Mt. Vernon and connects up to Rosslyn -- which can take you to Arlington, Georgetown or Pittsburgh). It's also a nice place to have a picnic or read a book (only 4-5 tables, so bring a blanket or camp chairs). The best part is, you can watch planes land at DCA....there's always a crowd doing it!