Grottoes

This vast, water-filled underground labyrinth can only be toured by boat.

A once-glowing grotto at the bottom of Waikapalae Wet Cave.

Countless grotesque faces stare out from this eerie Prague art wall.

This natural sea cave hides a small wonderland of natural turquoise beauty.

A grotto replicating one of the world's most famed Marian apparitions sits across the ocean from the original.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

The field of tiny caves that mark this Chinese cliffside are each their own historic Buddhist temple.

This serene oasis in an affluent Los Angeles neighborhood holds some of Gandhi's ashes and got Elvis into Eastern Philosophy.

The bluer than blue waters in these natural Israeli caves are reached via the world's steepest cable car.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

This collection of lurid religious statues tell the tales of a saint who stood down the devil.

A subterranean Holocaust refuge within one of the world's longest cave systems.

A wartime promise becomes a shrine to Our Lady of Lourdes.

A beautiful 62-acre Catholic shrine and botanical garden.

Rock-cut caves and 7,000 Buddhist sculptures carved into the nearly sheer face of a sandstone mountain.

A palatial sculpture park was built illegally and in secret by a self-taught artist over 36 years.

Grotto replete with mystical designs laid out in glued shell mosaics.

The glowing blue Nymphaeum of Emperor Tiberius.