Did the Aztec's built Tenochtitlan high in the Andes Mountains in a river valley?

No, the Aztecs did not build Tenochtitlan in the Andes Mountains. Instead, Tenochtitlan was constructed on an island in Lake Texcoco, located in the Valley of Mexico. This site was chosen for its strategic advantages, including access to water and fertile land. The city became the capital of the Aztec Empire before its fall to Spanish conquistadors in the early 16th century.