The Hilltop Reservation is a nature preserve located in Essex County, New Jersey, in the host communities of Caldwell, Cedar Grove, North Caldwell and Verona. It has over 200 acres (0.81 km2), and is the most recent addition to the Essex County Park System. It is composed of lands formerly occupied by the Essex Mountain Sanatorium, a hospital center originally constructed in the early 1900s to treat tuberculosis patients.