2 Best Sights in Terceira, The Azores

Climb deep inside an extinct volcano at this 1,804-foot volcanic cave located toward the middle of Terceira. You’ll be guided 148 feet down a set of stairs to the floor of the cavern before descending another 115 feet to a crystal clear lake fed by rainwater (which completely disappears during dry summers). Though the stairs are on the steep side, they have handrails and are not challenging to descend or ascend—just be sure to dress warmly, as the cave becomes colder and wetter the farther down you go. Along the way you’ll see unique stalactites and stalagmites. Opening times vary depending on the season, but are generally limited to a few hours in the afternoons, so check before you go.

This horizontal lava tube running 2,287 feet is worth a self-guided visit, as long as you wear good footwear and don’t feel claustrophobic in tight spaces. Navigating the sometimes dark, narrow, and low-clearance tube requires some ducking and squatting at times (you will be given a helmet for extra protection). Christmas Mass is held here when possible, hence the name.