The Old Post Office clock tower — that big tower in the Waldorf Astoria downtown — has reopened to the public after closing in October of last year. It's the third tallest building in Washington D.C., and the second highest 360-degree observation point accessible to the public in the city. The Clocktower & Museum at the Old Post Office is open from Wednesday through Saturday, 9 a.m. to noon, at 1100 Pennsylvania Ave., NW. Admission is free. #washingtondc #thingstodoindc #waldorfastoria #clocktower #postoffice