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

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

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

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

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

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

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

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

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.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Go inside to really appreciate this 500-year-old technological masterpiece.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

A reminder to choose water over wine since 1888.

A remnant from the golden age of aviation still in use today, Pan Am's Clipper service took off from this Art Deco gem.

This subterranean oyster house has been the pearl of Grand Central Station since 1913.

Imagine having a street run right through your home, or better yet, a historic bridge three stories high.

Need to book a room at the Hotel Pennsylvania? Just dial up 6-5000.

A famous songsmith's custom piano, dubbed "High Society," is hidden just out of sight in one of New York's finest hotels.

Harlem park dedicated to compulsive hoarders killed by their own junk.

The preserved house of a jazz legend still echoes with his music.

This Fifth Avenue church has long been the favored worshiping place of Broadway actors and vaudeville performers.