These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

12,000 sq. ft. museum tracing erotic art from antiquity to modern times.

Half of a waterfall goes into the river while the other half seems to disappear.

The "Fun Spot of the Desert" is now a haunting ruin, and a reminder that putting a water park in a desert is a bad idea.

This large midwestern cavern features impressive rock formations and an underground waterfall.

The ghost town that ended up on Ebay.

Houses are tucked between, on, and underneath giant boulders.

The only remnant of a small mining town is an abandoned railroad tunnel that is steeped in ghostly lore.

A unique waterfall that some believe attracts the fairfolk.

Thousands of well-dressed mummies below a monastery.

An unoccupied lighthouse encased in layers of ice from the waters of Lake Erie.

One of the most scenic falls in Massachusetts has a history of death and grim legend.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

The "world's biggest dinosaur" once housed a creationist museum in its abdomen.

Geothermal waterfalls in Tuscany.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

An ethereal glowing blue ocean cave in Croatia.

A curious collection of oddities including a lock of Alexander Hamilton's hair and Harry Houdini's ouija board.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

An eccentric garden of sculptures crafted in India decorate an Irish green space dedicated to Alan Turing.

Museum dedicated to awful artwork.

Witnessing the might of this dessert-colored desert waterfall is a rare, powerful treat.