Try not to get slimed in Tribeca.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

Ancient ruins hidden underneath a modern luxury hotel.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

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

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

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

A Nesting Doll of Churches.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

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

The underground sanctuary of a mysterious ancient cult.

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

2300-year-old Roman road connecting the empire.

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

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

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

A temple to modernity, tucked away amid Barcelona's more well known museums.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.

This cemetery features modernist statues as strange as its name.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

Inside a former cabaret, seven floors of erotic art.