Down a short, rough-hewn path from the woods near Druid Hill Park, a sudden expanse of the Jones Falls stream opens up to the 10-foot-tall, semicircle remains of a former grist mill dam. Falling into slow-moving, swirling patterns at the base of the man-made dam, the rushing water at Round Falls ultimately flow into Baltimore’s Inner Harbor. Even most Baltimoreans don’t know about the oasis in the middle of the city at Round Falls, let alone how to get there. Situated along the 11-mile Jones Falls hiking and biking trail,…