This loop is for hiking or biking. Nice scenery, wildlife, etc. I used the paved road to complete my loop because one section of dams had not been mowed in a long time. Although it was ridable, I really didn't want to risk running over a snake in that high grass. But this really is a good simple trail for a workout if you. A map can be picked up where you pay ($5) to get in. The St. Marks Unit of the St. Marks NWR is the location for the refuge head quarters and visitor center. A seven mile drive winds it way from the visitor center through fresh and brackish water impoundments and ends at the foot of the Apalachee Bay, near the historic St. Marks Lighthouse. Boat ramps, nature trails and a picnic area are located within this unit, and a road-side auto tour booklet is available for purchase in the visitor center. Uplands forests, forested swamps, fresh & brackish water marshes and a pristine salt water estuary ecosystem compose this unique area of Florida's Gulf Coast, making the St. Marks Unit a favorite for birders and outdoor enthusiasts alike.