Since the 1700s, this old barrel has acted as a post box that relies on the kindness of travelers.

The only quarter of the Old City not dedicated to a major world religion.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Named after one of Canada's greatest writers who lived out her days in this quaint neighborhood.

One of the largest underground systems runs under Canada's largest urban center.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

As the Dead Sea continues to deplete, massive sinkholes open along its banks.

A "miracle" that seems to produce more holy fistfights than holy revelations.

Oldest Protestant church in the Middle East, designed to resemble a synagogue.

Standing atop 2nd-century Roman ruins, this church is one of the oldest and most iconic in Old Cairo.

One of the most well-preserved temples of ancient Egypt.

Known as the Sistine Chapel of Egypt, this tomb houses some of the most well-preserved paintings in Egypt.

One of its engravings is believed to be among the first representations of medical and surgical instruments.

Ozymandias’ time-keeping temple.

A glowing underwater cliff attracts marine life and divers in equal measure.

These elusive, isolated rodents evolved into a distinct, locally iconic subspecies.

A glimpse of a waterfall is reached by a steel catwalk along a slot canyon located in an Ouray city park.

In the 1950s, two women saved this grand theater in the Colorado mountains from demolition.

The world’s largest concentrated solar plant generates as many problems as megawatts.

Brightly colored 30-foot-tall totems light up the desert sky just outside Las Vegas.

The wild west is still alive and well at this authentic mining town watering hole.

A monument celebrating the idea of reaching inaccessible places.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.