Plaques on its facade commemorate the Tiber's most destructive deluges.

A burial vault located under Tiber Island in the middle of the Italian capital.

This is the oldest Roman-made bridge in the city still existing in its original state.

An eclectic collection of thousands of items owned by the sculptor Frederic Marès.

18th century anatomical amphitheater of the Royal College of Surgery of Barcelona.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

Rome's first modern graffito is all that is left of a peaceful protest from the 1970s.

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

An 18th century fountain and two columns are all that remains of Rome's forgotten river harbor.

This curious, round temple is the oldest still-standing marble building in Rome.

This hidden alley near the location of Rome's first theater was the site of a curious miracle.

This ancient market is often referred to as the oldest shopping mall in the world.

A forgotten "city of water" underneath the famous Trevi district.

One of the most important yet well-hidden museums dedicated to the history of medicine.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

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

2300-year-old Roman road connecting the empire.

The underground sanctuary of a mysterious ancient cult.

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

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."

Charles Dickens was not a fan of the ghastly wall dressings in this 6th century church.

A Nesting Doll of Churches.