One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

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

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

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Elevated freight railway turned wildly successful urban park.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Macabre astrological automaton clock dating to the late 1400s.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.