Close to the waterfront is Boston’s  oldest “skyscraper,” the 500-foot tall Custom House Tower (3 McKinley Square, 617/310-6300, website , 7 a.m.–11 p.m.). Built in 1915, the distinctive Beaux Arts tower features a 22-foot-wide clock, and a pair of peregrine falcons who nest at its top during the summer. You can try to catch a glimpse of them, along with knockout views of the harbor, on the 26th-floor observation platform (tours 10 a.m. and 4 p.m. Mon.–Thu., 4 p.m. Fri., year-round, free).
Inside the tower is also a small museum with a few paintings and American historical artifacts on loan from the Peabody Essex Museum in Salem . The building was recently converted into one of Marriott’s more interesting urban hotels.