We found our new favorite place to hang out on cold days. After we found a parking space and made our way up the long ramp, a sweet little old lady greeted us at the door. She told us a brief history about the building. It was constructed in the early 1880's to house the United States Pensions Bureau. It was also built to commemorate the service of those who fought for the Union during the Civil War. It was the first all green building, and because the ventilation was free flowing through the windows up above, she said there were 8,600 less sick days. Yay for healthy peeps! She also said the National Building Museum has hosted 17 presidential inaugural balls. Even though I was loving the history lesson, my boys couldn't have cared less. They wanted to go and play. I've never seen them so happy! Happy babies=happy mamma!