San Franciscans leave gifts and messages for the magical beings that live behind the tiny, mysterious door installed on a tree in Golden Gate Park.

A hidden subterranean installation offers a view of the sky.

Art in the form of a winding, man made crack in stone.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

A historic hydroelectric power plant serves as the unusual backdrop for a public park.

This historic pink parlor keeps Phoenicians cool with homemade, retro ice creams.

Acres of natural wonders left behind by a socialite-turned-gardener.

This bizarre hotel on historic Route 66 has been plagued by rumors of paranormal activity.

According to legend, this tomb holds the secrets to time travel.

Once an indicator of social class, the color blue has come to define this city on the edge of the Thar Desert.

More than half of this Indian palace is drowned but it looks all the more spectacular for it.

The 953 windows undoubtedly make this the world's most beautiful screened porch.

This museum has a most unusual location: inside a giant, three-headed elephant.

Thailand's distressed elephants find peace at this Chiang Mai sanctuary.

This vibrant side road in Doha was painted light blue to reduce heat.

A pair of gigantic baby heads greet passengers at Atocha Station.

This small and often-overlooked museum holds some of Spain's finest artistic treasures.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

This ruined relic of the medieval city of Jahanpanah is a quiet oasis in the middle of New Delhi.

This hidden Sufi cemetery is a spiritual monument for India's third gender community.

A favorite haunt of Delhi's politicos and intellectuals, this old-school coffee shop was shut down under Indira Gandhi's Emergency.

This beautiful 16th-century necropolis marks an astonishing feat in heritage conservation.