Easy access to the airport and the city from the metro! You can take the blue or yellow just 2 stops to DCA. To get into the city, you're just 6 stops on the yellow line from L'Enfant Plaza, which gives you access to yellow, blue, orange, and green lines.
For an alternative way into the city (or over to National Harbor, where there's a giant ferris wheel), you can take the water taxi. Tickets vary from $17-$24 round trip per person, with children 2 and under free.