The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

This peaceful Massachusetts graveyard was one of the first "garden-style" cemeteries in America.

Walk in the footsteps of the gods and straddle two tectonic plates.

Iceland's tribute to its thankless civil servants.

This verdant, tree-lined Reykjavik graveyard is both enchanting and eerie.

This stunning concert hall has become a symbol of Iceland's national recovery.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

Hanging within this medieval church are the bones of a beast allegedly slain by a fourth-century saint.

Remnants of a 4th-century church with vivid medieval frescoes and ancient sarcophagi hide beneath this old basilica.

This landmark cemetery in Boston was created more than 300 years ago.

Civil War Fort on an island in the Boston Harbor.

A tiny town in an empty lot was the work of a local eight-year-old.

Pilgrimage site for star-crossed lovers.

A unique columnar residence built in the 19th century.

Eat first, shop later at this eatery within an Asian grocer.

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

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This cemetery served as the only official burial grounds in Cambridge for nearly 200 years.

Impossibly life-like natural history models created out of glass by a father and son.

Three prestigious academic collections come together to create a world-class natural history museum.

This tower commemorates the spot where George Washington hoisted the Grand Union flag.

A monument marks where a convent was burned by an anti-Catholic mob in 1834.