It got its name from the Spaniards thinking that it resembled a convent. There are four long buildings surrounding a courtyard of 260'x218'. There are 74 rooms for students, priest or soldiers. They aren't sure, but may be administrative. Built around 900-1000 with a rich combination of decorative motifs such as lattices, columns, huts, Chaac masks, snakes, owls, Venus symbols and human figures.A two headed feathered serpent coils through the whole frieze.