The oldest inn in England served brew to the crusaders.

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

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

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

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

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

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

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

Jesus' footprints and the first catacombs in the world.

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

2300-year-old Roman road connecting the empire.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

A Nesting Doll of Churches.

A simple plaque on the facade is the only reminder that the treaty ending the American Revolution was signed inside.

This bridge was constructed from the rubble of the infamous Bastille.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.