Some of my family came to visit this weekend, and we did a bunch of sight-seeing. Here are the distance estimates, this is definitely a lower-bound of the amount we walked. I tried to include walks that I know everyone did, and left off a bunch of random trips to the store. Distances are in miles.

Day 1 - Zoo and Fireworks

• 3.1998 to and through zoo
• 0.3037 from dupont metro to apartment
• 3.6359 to fireworks and back

TOTAL: 7.14

Day 2 - Smithsonian and Folk Festival

• 0.3037 from dupont metro to apartment
• 1.9614 Smithsonian and folk festival
• 0.3037 from dupont metro to apartment
• 1.0309 to play music and back

TOTAL: 3.6

Day 3 - National Cathedral and Arlington Cemetary

• 0.2353 apartment to bus stop
• 0.7487 at cathedral
• 0.6753 at Arlington Cemetary
• 0.3037 from dupont metro to apartment

TOTAL: 1.96

Day 4 - Library of Congress and Memorials

• 0.8012 at library of congress
• 3.3956 at memorials

TOTAL: 4.2

GRAND TOTAL: 16.9 miles

I'm guessing that adding in more detail could easily add another mile or more. In the end I bet we walked about 20 miles in all. When you trade a car for your feet, make sure you have good shoes!