Castalia Quarry Reserve Professional Review and Guide
"Located one mile west of Castalia, off OH 101, about six miles southeast of Sandusky. This trail circles the Castalia Quarry Reserve, a quarry site active from the late 1870s to the 1960s. In fact, you can extend your trip by riding directly inside the quarry bed. You won't need a lot of stamina for this ride, even though one spot on the trail is the point of highest elevation in Erie County. (Remember, this is northern Ohio.) From there, you'll be able to look out onto Lake Erie and catch a glimpse of South Bass Island.
You may also see the granite column of Perry's Victory and International Peace on the island. The trail is wide, and while you wouldn't want to take a shortcut into the quarry bed from the rim, you're still pretty safe from the edge. It's not fenced off, though, and you'll want to know how to ride a bike, or at least know where you brakes are."