Identify one major architectural achievement of the Maya.

The Stepped Pyramids are indeed one of the major architectural achievements of the Maya civilization. This architectural style is exemplified by structures like El Castillo at Chichen Itza, which features a four-sided pyramid with a staircase on each side. The design served both religious and astronomical purposes, showcasing the Maya's advanced understanding of mathematics and astronomy. The stepped design also allowed for the construction of expansive platforms for temples, demonstrating the sophistication of Maya builders.

Additionally, these pyramids often served as the center of ceremonial activities and were associated with important cultural beliefs, signifying the connection between the celestial and the terrestrial in Maya society. This achievement highlights the complexity of Maya architecture and their ability to create monumental structures that have endured throughout history. Other options in the question, such as the Great Wall, the Coliseum, and the Sphinx, are monuments from different cultures and time periods, which further underscores the unique architectural style of the Maya.