Chetro Ketl is the second largest Chacoan great house. It covers more than 3 acres and contains a great kiva and elevated kivas. As builders constructed second and third stories, they created an elevated plaza that stands 12 feet above the valley floor. Architectural design and large-scale engineering are typical of Chetro Ketl and other Chacoan great houses. Builders quarried rocks for construction, harvested timbers on distant mountains, and erected massive blocks of rooms during building episodes. The people built dams and canals, and engineered straight avenues and roads that crisscrossed the region and connected Chaco to distant communities. All these projects required complex planning, organization, and cooperation on a regionwide level. Succeeding generations carried on the work of their predecessors and created a unique vision of their world unlike anything before or since.