The old building on Calle Obispo Trejo is the original university the Jesuits founded in 1613, taken over by the state after their expulsion. The historic main hall and library are open to visitors on guided tours, which run several times a day in Spanish and weekly in English.
The library room with its leather-bound volumes and the Salón de Grados where doctorates were defended for three centuries are the highlights. The modern university has long since moved to a sprawling Ciudad Universitaria south of the centre, but the old building is still used for ceremonies.