The Massachusetts' State House was designed by Charles Bulfinch and built in 1798 to replace the old State House. The new State House is situated on top of Beacon Hill on land owned by John Hancock. It houses offices for members of the Senate and House, as well as various other government offices.
If you haven't been on a tour yet, it's probably worth checking out. The golden dome is as spectacular on the the inside as it is on the outside. Tours are free and last about 40 minutes. The first tour starts at 10:30am and the last tour of the day leaves at 3:30pm on weekdays. There's also a small bookstore on the first floor and plenty of public restrooms.