Originally an imperial tomb, Rome’s Castel San Angelo later became a prison and a papal fortress. Today it’s a museum where one of Antonio Gramsci’s elementary-school report cards is on display. In his lecture, “The Castel San Angelo in the Dyson Perrins Codex,” National Gallery Center for Advanced Study in the Visual Arts Dean Henry A. Millon discusses a 1575 plan to refortify the structure against both invaders and the floods of the adjacent Tiber. At 6:30 p.m. at the National Building Museum, 401 F St. NW. $6. For reservations call (202) 272-2448. (MJ)