If you are in Maryland, I highly recommend visiting Cunningham Falls State Park in the Catoctin Mountains, just west of Thurmont. There are 9 hiking trails ranging from easy to difficult. We chose the 3/4 mile cliff trail and had fun hiking through the woods, climbing over rocks, and exploring the Falls.
After exploring the Falls, we walked back to the beach at Hunting Creek Lake and cooled off in the water. The boys also played in the sand, building castles with moats while Doug and I relaxed on a blanket. We brought a picnic lunch, but couldn't resist buying the boardwalk fries with vinegar for an extra snack.