Garden of the Gods Park features the moderate, paved, wheelchair-accessible Central Garden Trail, a one-mile round-trip loop that passes between the towering Gateway Rocks into the heart of the park, where the scenery reflects a geologic history stretching back 300 million years. The ridges and cliffs began as horizontal sediments deposited as streambeds, sand dunes, beaches, and sea floors as environments changed, and about 65 million years ago stresses within the Earth pushed up the Pikes Peak Granite underlying the area. Pressure from this mountain-building bent, broke, and tilted the overlying sedimentary rocks into vertical positions, while the once deeply buried granite now forms the mountains west of the park. Over thousands of years, summer rains and the cycle of freezing water and expanding ice in spring weathered and eroded the upturned rocks into their present shapes, and these forces continue to sculpt the landscape. The park is also a crossroads of wildlife and plants from the Rocky Mountains, the prairie grasslands, and the southwestern desert, supported by milder winters than the mountains to the west, more moisture than the short grass prairies to the east, protective red rocks, and varied soils. Bighorn sheep can sometimes be seen on the rocky hillsides to the north, grazing higher in the mountains during summer and moving to lower elevations near the park in winter, making preservation of winter habitat increasingly important as development expands into their territory. The area's tall spires have long served as landmarks, and archaeological evidence indicates that people have hunted here for over three thousand years. The rock garden was a traditional camping place for the Ute and other American Indians, and in the early 1800's U.S. explorers and adventurers spread word of its scenic wonders. The 1850's and '60's brought goldseekers and then settlers who farmed and grazed cattle in nearby valleys, and with the coming of the railroad in the 1870s the first tourists arrived to see the unusual sandstone formations. Today the Colorado Springs city park is visited by people from many nations, while rules protecting visitors and the landscape prohibit climbing on dangerous rocks without technical climbing equipment, require technical climbers to register at the visitor center, warn of rattlesnakes in warmer months, and seek to preserve fragile native vegetation.