"One Hundred Brave Companions" - S2.E13

Before Tolkien dreamt of Middle Earth, there was once a place called Hollow Earth. It was quite the topic of debate in the 1820's. War of 1812 hero Captain John Cleves Symmes, believed the earth was composed of five concentric spheres. He stops by the Eagle Tavern trying to recruit the boys to join him on his voyage of discovery.