The Wind River Range is in the southern portion of the forest and is composed primarily of Precambrian granitic rock. Gannett Peak, the tallest mountain in Wyoming, is in the northern part of the range. Altogether eight peaks exceed and 119 rise at least above sea level. Fremont Peak, the second highest peak in the range, was originally believed to be the tallest mountain in the Rocky Mountains due to its prominence when viewed from the Oregon Trail by early pioneers. The Wind River Range is popular with mountain climbers because of its solid rock and variety of routes. The Cirque of the Towers in the Popo Agie Wilderness is one of the more popular climbing and hiking destinations, and an estimated 200 different climbing routes are located within the peaks that surround the cirque.