A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.

This ancient structure is widely thought to be the oldest intact pyramid in the world.

The subterranean sanctuary home to local shamans is a sacred site for people of all religions.

Sunset-colored dunes of volcanic ash make taking a poor photo impossible.

A shining sculpture made of 3,115 lights, the number of visible stars in the Northern Hemisphere.

This research hub in the Amazon Rainforest is perched amid one of the world's most biologically diverse landscapes.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

An architect's childhood fantasy treehouse made real.

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

The residents at this Yellowstone wildlife park will certify your cooler as "bear-proof."

This permanent exhibition celebrates the finest of our heartless automatons both real and fictional.

The traditional houses along the coast of this charming Japanese fishing village allow people to sleep above the sea.

This gallery of prehistoric red ochre art lines the wall of a scenic segment in Utah's San Rafael Swell.

Croatia's "hairy stone" fortress is one of the most well preserved Istrian castles.

This former Texas landfill is flush with 300 million-year-old fossils, all fit for the taking.

A natural history wunderkammer in the middle of the desert.

A giant toy jack made of numerous welded-together fire hydrants.

Travelers leave tea kettles in a remote part of Death Valley as part of a mysterious, decades-old tradition.

A whimsical village of unique treehouses resides in a Washington forest.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

These ancient sunken lanes were naturally tunneled into the soft ground by countless footsteps.

Football field-sized microalgae production tanks on the Hawaiian coast create a stunning view from space.