The Olmstead Brothers, the sons of the man who designed Manhattan’s Central Park and Boston’s Emerald Parkway, designed this 1,800-acre park. The park features an ancient stone tower, dedicated in 1900, which can be climbed for panoramic views and is listed as a National Historic Landmark. Hiking trails lead visitors to Castle Craig, which is open from May 1 through October 31, 10 a.m. to 4:45 p.m.