The final resting place of the poets Shelley and Keats.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

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

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

A Nesting Doll of Churches.

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

A fortified medieval basilica on the Caelian Hill preserves extraordinary frescoes and one of Rome's most beautiful hidden cloisters.

2300-year-old Roman road connecting the empire.

Believed to be the remains of the lost Temple of Minerva, this nymphaeum has been known by its misnomer to this day.

One of seven Jewish catacombs in Rome and one of only two open to the public.

Jesus' footprints and the first catacombs in the world.

Roman politician Herodes Atticus built this nymphaeum to honor his wife, whom he may have murdered.

An abandoned Roman salami factory has found new life as an art space home to 200 squatters.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

An unassuming secret door once led to a legendary watering hole.

The oldest surviving synagogue in New York City is now a soaring art space.

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

Nondescript elevator doors open to reveal a stunning, surreal world.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

A restaurant on Staten Island showcases a different grandmother’s cooking every night.

The abandoned husk of a mental institution that failed to save a Jazz Age icon still sits nearly unchanged.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.

A very classy 1920s-era bar right in Grand Central Station.