I'm stuck in Boston for 12 hours, what should I do?

I had a great time, i eventually made it to the pig slide, it was neat but i have no idea how he got so fast. checked out the street markets near government center, that was fun. Some guy with a violin started following me around, i had my own soundtrack for a while, that was cool even though it sounded sad. Found the greenway, that place is pretty awesome. A lady slapped a cheap bracelet on me and bullied me to give her money. Checked out the freedom trail and got humbled. The park with the giant MLK arms had Shakespeare stuff going on, that was neat. Watched a street performer do a balancing act. There were cow statues...everywhere. I may need some elaboration on the cow statues. Tried to figure out if i should buy a 10 ride T pass or just pay as I go, panicked about getting stuck somewhere and ran away. i really wanted to get to the museum of science and the USS constitution but i started freaking out missing my flight so I got to the airport 3 hours early and everything went fine. Excited to come back here, thank you all for the suggestions.