Quincy Market and Faneiul Hall; the harbor boat cruise is awesome, but costs a little; the Freedom Trail is a great way to walk the city; Paul Revere's House is awesome and cheap to see; you MUST walk through the Commons and the Public Garden - the Cheers sign is across from the Garden on Beacon Hill - and there's a great city tour where you can jump on and off the trolley all day at about 15 different spots throughout the city.
There's so much to see there, I've been there twice and still haven't seen everything I wanted. It's gorgeous, too. And the natives are friendly. I had a guy see me looking at a map out on the street, and he took about 15 minutes to tell me good places to check out and which subways would get me there.
If you love history definitely the Freedom Trail. Eat at the Union Oyster House, one of the oldest restaurants in the United States. Visit the Gardner Museum, scene of the largest art thefts in American history, if you love art. The North End is filled with incredible Italian restaurants. The South End is hip and trendy. Window shop on Newbury Street. Of course Fenway Park and the Red Sox.
I would like to suggest you to take the Freedom Trail. This 2.5 mile trail leads you through 16 of the top historical highlights of Boston on an easy to follow red path. It’s pretty neat – you can start anywhere on the trail and take part of it or all of it.
All great suggestions. Take a tour of Fenway Park or better yet go see a game. Science Museum is great as is the Museum of Fine Art. The Freedom Trail, Bunker Hill, the Boston Common, Faneiul Hall, so much to see and do. For a quick day trip go see Plymouth Rock on your way to the Cape for a day. Take a boat tour of Boston Harbor or go on a whale watch. So much to see. Have a great time.
Fantastic suggestions so far. Definitely Quincy's Market is a fun place to spend some time. Boston Commons. Cheers is a fun place. If you like history and literature, I would take a short trip to Concord. It's packed full of American and literary history. Some of the best American literature and important essays were penned in this area. Have fun! Be sure to eat at one of the restaurants in the North End. I love Boston and the surrounding area. Next to New Orleans, it's my favorite city (to visit) in the US.