The Capitol of Puerto Rico is a domed neoclassical building on the Atlantic side of Puerta de Tierra, just outside the old city walls. It was finished in 1929 in white Georgia marble and modelled, loosely, on the US Capitol in Washington. The rotunda holds mosaic murals of major moments in Puerto Rican history and the original 1952 constitution of the Commonwealth is on permanent display in a glass case.
The Legislative Assembly meets here, but the rotunda and the public galleries can be visited free Monday to Friday with ID at the entrance. Guided tours run in English and Spanish on request. The marble steps facing the ocean are a fine place to watch the sun set; you can walk back to Old San Juan along the seawall promenade in twenty minutes.