Mirror Lake State Park is a 2,179-acre (882 ha) Wisconsin state park in the Wisconsin Dells region. The process of establishing the park began in 1962 and the park officially opened on August 19, 1966. It contains Mirror Lake, a narrow reservoir with steep sandstone sides up to 50 feet (15 m) tall. The lake has a surface area of 137 acres (55 ha) and an average depth of 10 to 14 feet (3.0 to 4.3 m). Recessed out of the wind, the water of Mirror Lake is usually calm and often as glassy-smooth as a mirror, hence the name. Situated in a major tourist area, the state park has an extensive campground and other visitor amenities. Also located within the park is the Seth Peterson Cottage, a Frank Lloyd Wright-designed building available for public rental.