Complex sentence: A tram takes visitors up to what was formerly called the "Fairy Caves", now known as the Glenwood Caverns, which is a complex cave system that travels through the bowels of Iron Mountain.
Split into simpler sentences: A tram takes visitors up to what was formerly called the "Fairy Caves", now known as the Glenwood Caverns. The Glenwood Caverns is an incredibly complex cave system that travels throughout the bowels of Iron Mountain.