Mashomack Preserve is one of my favorite hiking locations. Its on Shelter Island and is enormous. Its over 2000 acres of incredible land with untouched beaches fresh water marshes and woodlands. Nearly all of Long Islands trees were cut down for building efforts and its my theory that most of the Mashomack wooded areas are untouched. Its just not like most other areas of Long Island. If you make a trip be sure you take the obvious hiking gear. Bug repellent, GPS, map, water and make sure you leave enough time to get back.
Be sure to check out Nichols cemetery. Its beautiful, well kept family cemetery for the family that lived in the area. Its hidden pretty well and easy to miss. I took many pictures.