The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The pioneer of psychoanalysis spent the final year of his life here, still seeing patients on that famous couch.

A man-made island in scenic San Francisco Bay.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

San Francisco's newly reopened hands-on science museum.

Legendary frontman of the Doors looms in this giant mural by famed Venice muralist, Rip Cronk.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

For centuries no one knew there were hundreds of bones and precious artwork hidden beneath this Swiss church.

An adorably sweet display of sculpted Precious Moments figurines.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

This $62 million dollar temple was erected to house one little dental fragment of religious history.

Terrapins of all colors and shapes are quick to bring fascination (and possibly long life) at this museum.

Singapore's landscaping project is home to 18 incredible Supertrees.

This beautiful, historic church looks like something out of a simpler past.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This stunning concert hall has become a symbol of Iceland's national recovery.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

The most powerful waterfall in all of Europe.

Climb right into the heart of this colorful Iceland volcano.

An encyclopedic collection of mammal penises.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.