The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

One of Ireland's most infamous prisons for rebels including men, women and children.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Macabre museum devoted to historical Viennese murders.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

The topiary maze at the Habsburg hunting lodge.

An artsy hidden staircase leads to breathtaking views of San Francisco.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

A surrealist timepiece by the artist of melting clocks.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

Notorious artist squat renovated into legal studios.

The remains of the first punk club in L.A.

Dozens of lights dangle from the branches of what may be the brightest tree in Los Angeles.

Rainbow-hued local gem in Venice.

Hidden in the hills of Hollywood, this secluded Oz-themed garden is dotted with dozens of thrones.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

Medical and zoological curiosities for sale.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

World's largest collection of serial killer artwork and other macabre exhibits.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

This beautiful Victorian ironwork masterpiece was built to keep London from smelling like poop.