Built between 1537 and 1540, this was one of Mexico’s earliest monasteries and its church – the city’s cathedral – has a beautiful Moorish-style wooden ceiling. It's up a shaded path from the southeast corner of Plaza Xicohténcatl.
Just below the monastery, beside the 19th-century Plaza de Toros (bullring), is a capilla abierta (open chapel) with three unique Moorish-style arches. One of the entrances to the grounds is locked, but you can get close (though not enter) the capilla from other gates.
Museo Regional de Tlaxcala, housed within the monastery building, has a large collection of religious paintings and sculptures and some pre-Hispanic artifacts from nearby archaeological sites.