These hut foundations are believed to be the residence of Romulus, founder of Rome.

A Nesting Doll of Churches.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

St. Francesca Romana, patron saint of drivers, resides in the church she founded.

Jesus' footprints and the first catacombs in the world.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

A magnificent waterfall is also home to the remains of a Roman hydraulic engineering system.

The yawning maw of this pagan visage is said to bite off the hands of liars.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Architectureal fantasy quarter of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A resilient tree that has survived for more than 700 years in Guánica Dry Forest.

The short hike is worth the stunning views and crystal blue waters of a secluded beach.

Drift through underground caves on a tube.

Built some 700 years ago, this Taíno ceremonial site features ball courts, petroglyphs, and evidence of ancient astronomy practices.

The highest peak in Puerto Rico is home to a rare fern that can only be found on six trees at its summit.

This rock in the middle of a river in Jayuya contains dozens of Pre-Columbian Taíno petroglyphs.

Ancient petroglyphs discovered only after a massive fire swept across Michigan in the 1880s.

Deep scars on the earth left by the Ice Age.

Halloween spirit is alive and well in this small town, where residents race motorized caskets in a yearly tradition.

The world's oldest operating jazz club has been in operation since May 1934.