Within the park boundary, Yosemite can be divided into regions. Located in the western end of the park, Yosemite Valley is about eight miles long and a mile wide. The Merced River flows through the glacial valley and is the hub of tourist amenities. At an elevation of around 9,000 feet, Tuolumne Meadows at the eastern border is sub-alpine meadow known for its polished domes, and is a popular climbing destination. The Hetch Hetchy Valley is another glacial valley in the northwestern region of the park. The reservoir, which supplies San Francisco with water, was the source of environmental conflict in the early 1900s.