Complex sentence: It is not only unique to Chaco Canyon, but also to Ancestral Puebloan architecture as a whole, with "no comparable features" in the region; the nearest similar structure is located more than five hundred miles away at Casas Grandes, in Mexico.
Split into simpler sentences: It is not only unique to Chaco Canyon, but also to Ancestral Puebloan architecture as a whole. The nearest similar structure is located more than five hundred miles away at Casas Grandes, in Mexico.