The first public library in the Americas has more than 45,000 books dating back to the 15th century.

This "City of Books" holds a museum, library, and the complete personal book collections of five of Mexico's greatest thinkers.

This popular cave pool is truly magical, despite the crowds.

This foreboding building was the headquarters of the terrifying Spanish Inquisition in Mexico.

The meteor that sealed the fate of the dinosaurs landed at this site, one of the largest impact craters in the world.

The ruins of an ancient temple to the Aztec wind god discovered in the middle of a metro station.

This strange sculpture of a menacing skull surrounded by sun rays was discovered at the foot of the Pyramid of the Sun.

The largest cave shaft in the world is home to thousands of birds and popular with BASE jumpers.

These haunting ruins of a 700-year-old Prehispanic city have witnessed centuries of wars and massacres.

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

Explore the atmospheric ruins of an abandoned convent in the dense forests of Mexico's first national park.

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

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

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

These azure waters were thought to lead to the Mayan Underworld.

Part bookstore, part café, and part forest.

Hidden within this iconic mountain are a set of World War II bunkers once used by German forces.

Ever hear of the Milazzo Cage?

One of Rome's most picturesque and original bridges was also a popular choice for Grand Tour artists.

A massive marble foot is tucked away in a small alley near the Pantheon.

This basilica is dedicated to two saints, one of which is known more for his famous quote.

A deep mark on the remains of a Roman temple, believed to be left by a legendary warrior.

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.