Complex sentence: It was much smaller than classic cities such as Teotihuacan and Tikal, or later cities such as Tenochtitlan and Cholula, although at the time it may have been the largest city in Mesoamerica.
Split into simpler sentences: It was much smaller than classic cities such as Teotihuacan and Tikal, or later cities such as Tenochtitlan and Cholula. Although at the time it may have been the largest city in Mesoamerica.