A small underground archaeological museum behind the cathedral that excavates twenty centuries of Valencian history in a single rectangular pit. Roman baths, the curia of the Republican forum, a Visigothic cathedral, the foundations of the Moorish alcázar, and the medieval almshouse that gave the museum its name all sit on top of each other. The glass-floor entrance lets you see down into the trench from street level.
A good half-hour visit and one of the city's best stories. Especially worth combining with the cathedral and Plaza de la Virgen, since you walk out onto the same square.