Sometimes called the New State House, this seat of the Commonwealth's government was built in 1798, on property that belonged to the first governor, John Hancock. Overlooking bustling Boston Common, the State House is hard to miss with its distinctive gold-plated wooden dome.
If you go:
Public tours are available on weekdays, offering an informative and entertaining look at history and government. Of particular interest is the lore of the carved wooden cod that is kept scrupulously on display when the legislature is in session.
Links:

2 Beacon St.
Boston, Massachusetts 02133 USA
Phone Numbers:
Guided Tour Information
+1 (617) 727-3676
+1 (617) 727-3676