The Marble Hill Natural Resource Area is a beautiful 288-acre preserve located just north of Phillipsburg along the Delaware River. Owned by the County of Warren, the area is managed for conservation and public use in partnership with several nonprofits including the New Jersey Youth Corps, The Highlands Community Service Project, and the Metro Trails hiking group.
This park not only provides watershed protection to the Delaware River, but it also provides coverage for neo-tropical song birds and other migratory song birds that use the Delaware River as a flyway during migration. The site offers a wide biodiversity of upland deciduous forest, stands of rhododendron that are particularly colorful in the late spring and early summer, and about 4 miles of trails offering seasonal vistas of the Delaware River. Passing through the park is a popular section of the 32-mile Warren Highlands Trail which meanders across the county highlighting various sites of interest along the way.