Sugarloaf is a private park northwest of Washington, DC between Gaithersburg and Frederick, MD. You'll see it in the map below near I-270. It is a favorite hike to get away from the city. It's fairly close to the city but the feel is remote and rustic. There is no water available at the facility that I remember. There are shelters which have a concession stand that operates during certain hours/months. There are places to rock climb, stairs to hike and a fire road for easier traveling. The view from the top is impressive.