The Greater Boston Convention & Visitors Bureau maintains two visitor centers:
Boston Common Visitor Information Center: 148 Tremont St (at Winter; T: Park Street). M-Sa 8:30AM-5PM, Su 10AM-6PM.
Shops at Prudential Visitor Information Center: 800 Boylston St (Center Court; T: Prudential or Back Bay). 9AM-5PM daily.
The National Park Service also maintains two visitor centers as many of the historic sites in Boston are considered part of the Boston National Historical Park:
Downtown Visitor Center: 15 State St (behind the Old State House between Devonshire and Washington; T: State Street), 9AM-5PM daily.
Charlestown Navy Yard Visitor Center: Navy Yard Pier 1 (next to the USS Constitution). 9AM-5PM daily (until 6PM in July and August).