Plaza de Toros de Las Ventas is a real time commitment — fit it in only if it's a priority.
Allow 1–1.5 hours (tour).
Architecturally it's a stunning Moorish-revival arena, and the guided tour or museum gives real insight into a contested tradition. The catch is the obvious one: an actual corrida involves the killing of bulls, which many visitors find ethically unacceptable — the building impresses, the spectacle divides hard.