Colorado's Chimney Rock named National Monument WASHINGTON (Reuters) - Colorado's Chimney Rock, an archeological site spiritual to Native Americans, was named a national monument on Friday by President Barack Obama. The 4,726-acre (1,912-hectare) site in southwest Colorado holds the ruins of hundreds of structures built by the Pueblo people about 1,000 years ago. They include the highest-elevation ceremonial "great house" in the southwestern United States, the White House said in a statement. Chimney Rock draws thousands of visitors who seek out its rich cultural and recreational opportunities. Today's designation will ensure this important and historic site will receive the protection it deserves," Obama said. Chimney Rock is a promontory about 315 feet tall within the San Juan National Forest. It is surrounded by the Southern Ute Indian Reservation. Every 18.6 years, during the northern lunar standstill, the moonrise is aligned with the site's two rock pinnacles, as well as during the summer and winter solstices, and the fall and spring equinoxes. Pueblo descendants return to Chimney Rock to commune with their ancestors and for other spiritual and traditional purposes. Chimney Rock's designation as a national monument is the third Obama has made under the Antiquities Act. The other two are Fort Monroe, a Civil War and military site in Virginia, and Fort Ord in California.