I was just up there on Labor Day hiking around the area from Millbrook/Van Campens Glen up through Flatbrookville and as far north as the Inn. I agree, there is a lot to see, from the relatively recent stuff resulting from Tocks Island (Rock cores, remains of Lake Success [Crater Lk], and Blue Mountain Lake development), to the much older sites such as Old Mine Rd itself, the various cemeteries, Van Campen Inn, Pahaquarry Copper Mine, ruins etc. It’s an excellent example of nature reclaiming once populated areas. There’s of course plenty of natural areas as well though, Sunfish Pond, and the various lakes, views, etc that can be found all along the ridge and in the valley.
A few weeks before that, I was up there again but more in the Walpack and Layton areas, which has its own attractions as well. The village itself, Buttermilk Falls, etc.