The Palisades are a natural red sandstone cliff formation that defines the northern edge of Santa Monica Beach and separates the shore from residential neighborhoods above. Access to the beach from the Palisades was made possible by the construction in 1875 of the "99 Steps" at the base of Arizona Avenue. Another access point was provided by the Thompson Scenic Railroad, a 500-foot long undulating track that used gravity to transport guests to and from the historic Arcadia Hotel. The California Incline built in the 1920s continues to provide vehicular and pedestrian access between the beach and the city above.