10901 Scarlet Tanager Loop, Laurel, MD 20708. Free, with ample parking and restrooms at the visitor center, the main lot, and the Cash Lake Fishing Area. We'll link the Cash Lake, Valley, and Fire Road trails for a full loop past two lakes and through mature forest. Watch for the beaver lodge on Cash Lake and use the two camouflaged wildlife blinds — bring binoculars if you have them; late April is peak spring migration. Established by FDR in 1936, this is the only national wildlife refuge in the country created specifically to support wildlife research.