There are a number of parks and trails near Monroe, NY.

I'd recommend:

Anthony's Nose - moderate trail with great views of the Hudson River

Harriman State Park: Some trails lead to viewpoints where Manhattan can be visible on clear days

The Catskills - tons of great hiking/rock climbing within an hour or so drive from Arrow Park!

Storm King Art Center is a 500-acre outdoor museum located in New York’s Hudson Valley, where visitors experience large-scale sculpture and site-specific commissions under open sky.

Great for history buffs or those who simply want beautiful views of the Hudson River

Did you forget to pack your suit? Good thing there's an outlet mall down the road!