Sugarloaf Mountain and Urca Hill Natural Monument Mountain, then an island, on 1 March 1565. The site was chosen to guard the entrance to Guanabara Bay, and the mountain was important as a signalling point. A landfill connected the island to the mainland in 1697, and various buildings were erected to defend the territory, but the Urca urban neighborhood was only built 300 years after the city was founded. The Sugarloaf Mountain and Urca Hill Natural Monument was created by the city of Rio de Janeiro by municipal decree 26578 of 1 June 2006. The objectives are to guarantee green spaces for leisure in a natural area,
Sugarloaf Mound Nation wants to build an interpretive center to the north of the mound, on property now owned by the Missouri Department of Transportation. Sugarloaf Mound Sugarloaf Mound is the sole remaining Mississippian culture platform mound in St. Louis, Missouri, a city commonly referred to in its earlier years as "Mound City" for its approximately forty Native American earthen structures. Sugarloaf Mound is the last remaining of the mounds built within present-day St. Louis by a Native American culture that thrived in the area from A.D. 600-1300. The mound itself is the oldest human-made structure in the city of St. Louis.