The southern portion of Governors Island includes a park that covers more than 43 acres (17 ha). The north end of the park contains Hammock Grove, a landscaped area of rolling hills with over 60 tree species. The south end of the park contains the Hills section of Governors Island, which covers 10 acres. The Hills consists of four hills that are 26 to 70 feet (7.9 to 21.3 m) high, and are made partially of reclaimed debris from the demolition of the island’s former residential towers. The Hills cost $70 million to build; the construction of the Hills was funded in part by Google CEO Eric Schmidt, who donated $15 million.