Mirrors and glass shards cover every inch of this arrestingly beautiful mosque.

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

Small museum packed with artifacts recovered by the man rumored to be the real-life inspiration for Indiana Jones.

The remains of diamond fever taken over by the desert.

The hallucinogenic center of the ancient world.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

Started as a kitchen garden, now the second largest botanical garden in the world.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Explore 10 acres of environmental sculptures.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

Stalactites and stalagmites in a beautifully lit cave.

The world's longest known cave system.

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

Stunning wetlands ablaze with pink lotus flowers.

The first declared National Monument in the United States.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

Hot springs monkey spa in the middle of Hell's Valley.

An emerald-green grotto just a short trip from Austin.

Rippling sand dunes frozen in the Arizona rock.