Hook Mountain. Rte 9W, North Nyack, NY. For the fall hawk migration, Susan says it's better than Hawk Mountain in Pennsylvania. (The peak of the broadwinged hawk migration is 15 September.) Use the parking lot of the executive golf course in Rockland Lake Park (go around to the right when entering the park). The yellow trail starts (very inconspicuously) at about 2 o'clock when standing in the circle facing the clubhouse. Take this trail to the T junction with the ridge trail; turn right.
Rockwood Hall. Rtes 117 & 9, North Tarrytown, NY. Formerly the site of a Rockefeller home; grounds open to the public. Terrific views of the Hudson and the Pallisades.
Old Croton Aqueduct Trail. Croton Dam to the Bronx. The best nature-walk part is from the top of the dam, on the eastern side, south to Crotonville. The best houses to see along the way are from Tarrytown at Lyndhurst south to Dobbs Ferry. The part south of there, down to the area of the Hudson River Museum, has the good views of the Hudson and the Palisades.