A short 2.2 miles away from Antietam Lake on Antietam Road is the Earl Poole Sanctuary.
A chain (not locked) was draped across the entrance so I parked and walked around it. The sign conspicuously says its open to the public dawn to dusk, but I haven't figured out the parking situation yet. I wouldn't even say that there is a parking lot per-se, just a big mowed field beyond the chain.
The aged barn and picnic tables are iconic fixtures that draw you in once you enter the area. Short trails branch out in three directions from the barn.
A nice variety of eco-diversity is just a short distance down the Woodlands Trail. A 1/4 mile walk along the little creek cuts sharply into woods and up a hill to a wetlands, more like a seep caused by a spring. It's very rocky and wet at one spot too.