I stumbled into the incredibly packed Japanese Street Festival at 12th Street and Penn Avenue on this beautiful weekend day. Tourists and festival goers packed the streets and huge lines formed for the food vendors. About.com has a great description of this free annual event:
"The Sakura Matsuri Japanese Street Festival is a free major event of the National Cherry Blossom Festival in Washington, DC. It is the biggest Japanese street party in the nation. The festival stretches six blocks and includes Japanese performances on five stages, 20 Japanese and Asian restaurants, 30 interactive cultural exhibits and 35 vendors selling Japanese products."