Perhaps the most spectacular grotto along the Algarve coastline.

Many generations of travelers have passed through the steep, smooth walls of this canyon.

A grove of "candelabra redwoods" deep in California's Lost Coast.

Neither Spanish settlers nor anyone since has been able to tell who built these strange California rock walls.

For six months of the year, three giant mirrors direct a pool of sunshine onto this otherwise occluded town.

A Prada store in the West Texas desert that is never open for business.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

Less a museum than a bizarre fantasy world created by artists and engineers.

Flying high, this unusual hornet statue celebrates the local soccer team formerly owned by Elton John.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

The uniquely-designed winter home and sculpture studio of Anna and Archer Huntington.

England's "pier at the end of the universe" unites astronomy and contemporary architecture.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.

See the sky in a new way through this art installation.

A view-altering observatory at the University of Texas.

A hidden subterranean installation offers a view of the sky.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

Artist James Turrell's ode to dawn and dusk on the campus of Rice University.

This traditional Japanese-style house doubles as one of James Turrell's colorful works of art.

Seattle's own bad art museum located inside Cafe Racer.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

A trio of giant wooden megaphones turn up nature's volume in this Estonian forest.

This elaborate towering structure was once famed for its revolutionary height.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.