Venture into the past with an unlisted exhibit hall featuring extinct birds.

These warring psychedelic crags commemorate an unsuccessful military operation.

A salty red wasteland in Tanzania is a breeding spot for endangered flamingos.

A mixture of strange symbols, ciphers, words and cryptograms carved in 1876 remain unsolved to this day.

A 1970s resort city now stands abandoned, caught in the middle of a divided island.

Not far from a popular beach, an unfinished, abandoned mansion for Bulgaria's last communist dictator.

The oldest still-existing mosque in the United States sits in a remote prairie in North Dakota.

This whimsical stacked cabin looks like something out of a children's book.

A giant scrap metal troll rests his hands on top of a dilapidated building covered in graffiti.

This ruined fort and statue are a testament to the last king of Kaua‘i’s savvy diplomacy skills, which briefly brought Russians to Hawai‘i.

Only 68 people per day are allowed to visit this New Zealand bird-watcher’s paradise.

This Connecticut ferry has been operating in some form since 1655.

After several weeks of radio silence, this abandoned oil tanker washed up on a remote beach in Liberia.

A ghostly mansion in the middle of downtown Tunis.

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

The medieval ferry service has been going strong since the 14th century.

The tallest mud-brick structure in the world has been standing since the 1500s.

Hidden in the hills is a mysterious stone structure, known only to a few.

Once a safe haven for locals engaged in blood feuds, this 400-year-old fortified tower is now a museum showing what life was like for those lying in wait within its walls.

North Korea's massive "hotel of doom."

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

For millennia, explorers were obsessed with discovering the source of the Nile—is this small mountain stream really the answer?

Recovered from the brink of extinction, at home in the Financial District.

Far from the shore, this sandy victim of the Skeleton Coast looks like it was plopped in the middle of the desert.