The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

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

A huge enchanting public park just outside the ancient walls of Rome.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

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

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.

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

A Nesting Doll of Churches.

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

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

Architectural monsters are devouring this palace's every door and window.

An alchemist's "magic door" stands in the middle of a Roman park.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

An almost life-sized elephant named Ms. Ellie greets visitors at this jumbo-themed museum.

A daily replay of the experiment that proved the rotation of the Earth.

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

Contrary to what one might expect, ice forms inside this small cavern during the summer and melts during the winter.

A local prank turned town icon.

This elaborate towering structure was once famed for its revolutionary height.

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

Yo, Adrian!