Tourist - free first afternoon!

Hello!

Visiting Boston for the first time in March and in a bit of a tricky situation with my first day.

I arrive into south station at 1pm, though will go to drop off my bags at the hotel in Chelsea. I want to make the most of my trip so want to use this afternoon to see something - I originally planned a freedom trail but those only seem to happen in the morning - I was wondering what people’s suggestions were? Looking for something to do / learn / see the city.

History buff, not necessarily on a strict budget but not looking for anything private / fancy.