Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

After the famous composer died in Paris, his sister snuck his heart out of the country to honor his wish that it be buried in their native country.

An underground city of salt.

An Irish Memorial commemorating those who perished due to potato blight.

This black shoreline is made up of exploded lava particles.

Watch the newest land on the planet form before your eyes.

Hide from the tourist hordes in these relatively unknown, and unguarded lava caves.

Home of Howard Hughes' Spruce Goose.

On the Oregon coast there is a natural hole that seems to be draining the sea.

Now containing the bones of the actual conquistador, instead of someone else.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

An elaborate shrine dedicated to the four corners of the world unfortunately misses its mark.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

Every equinox this Maya pyramid puts on a spooky ancient light show.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Morocco's largest Jewish cemetery.

An awe-inspiring mosque in Morocco with one of the tallest minarets in the world.

Traditional 11th-century outdoor tannery.

Mosaics, storks, and brothels—this ancient city has it all.

Founded as a refugee camp, now a popular tourist spot.

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

Olfactory delights in San Francisco's Botanical Gardens.