The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

A 220-foot deep watery drop-off, filled with marine life.

Collection of fossils, plants, and ancient animals encased in amber.

A small burial plot formerly stranded in the middle of a road.

An immense cave that has served as an outlaw's treasure trove, an underground dance hall, a nuclear fallout shelter, and much more.

This beautiful grotto is one of those places where you can't believe you're just outside Austin.

An emerald-green grotto just a short trip from Austin.

This eclectic Austin curiosity shop is home to all things strange and unusual.

DIY collection of eclectic holdings.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

Continuing the tradition of the dime museum in style.

It took 275 years and four burials to finally put the Mayflower’s most famous passenger to rest.

The universally beloved children's television figure is interred on a high hilltop in one of western Pennsylvania's oldest cemeteries.

Sloth rehabilitation center in the jungle of Costa Rica.

This collection features more than 240 antiquarian maps from around the world, in addition to historical views and plates focusing on North Florida.

A sprawling maze of used books piled from floor to ceiling.

After serving in Vietnam, Korea, and even a stint in the Turkish navy, the unique ship is now open as a museum.

These ruins are all that remain of what a Spanish barrack that likely housed a quarry overseer, masons, and stone cutters involved in the construction of the Castillo de San Marco.

The graves in Florida's oldest Black cemeteries are marked with shells, stones, and mementos of the deceased.

St. Augustine's record-setting narrow street was designed to protect against pirates.

Home to the Amorphophallus titanum "Corpse Flower," which is among the largest flowers in the world and also smells powerfully of rotting flesh when in bloom.

The remains of a World War II munitions factory still haunt the fields of this Twin Cities suburb.

The highest dunes in California are the most likely place in the area to hear the Singing Sands.

This ancient cave is home to a museum, bar, and is filled with fluorescent minerals.