Five and a half miles southwest of Ithaca, the biggest state park in the area offers extensive trails and a very popular swimming hole (late June to early September). Treman's gorge trail passes a stunning 12 waterfalls: don't miss Devil's Kitchen and Lucifer Falls, a multi-tiered wonder that spills Enfield Creek over rocks for about 100ft.
There's also camping here from $18 per night per site and a few cabins (from $60).