Agreed. But, isn't the Capitol closed (for lack of a better description) closed on Sundays. I know the Capitol Visitor Centre is closed on Sundays and there are no guided tours on Sundays.

Sorry I should have been more careful with my choice of place names.
I didn't mean going inside the Capital Building so much but more seeing the area nearby...the reflection pools, passing the white house, taking some photos of the bit at the end of the reflection pools, etc.

Still, it sounds like I should store my luggage somewhere rather than pull it around...don't want to get stopped every 5 minutes.

Which begs the questions, do I store it at DCA or would somewhere else (like near the bus station for getting to IAD). I suspect DCA if I want to take a taxi?

Luggage storage in DC is challenging, and is unavailable at DCA or IAD.

last i heard, there was still luggage storage available at union station.

metro yellow line>red line. the walk to the capitol grounds from union station is pretty. if the botanic garden is open that day, and to your liking, it is a lovely place.

You could also consider proceeding directly to IAD, checking-in, and then visiting the excellent Steven F. Udvar-Hazy annex of the Air & Space Museum.

You can explore transportation options between IAD and the museum here:

http://www.nasm.si.edu/visit/transpo...n/airports.cfm

You might be best off renting a car for the day, picking it up at DCA and dropping it off at IAD. That would handle your luggage storage nicely and may not cost more than other transportation/storage options.

+1 on this suggestion. The indoor Conservatory and outdoor National Garden (and Bartholdi Park across the street) are a delight in all seasons. And they are open 10am-5pm every day of the year.