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

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

Every autumn, this hillside is ablaze with red summer cypress.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

The intended purpose of this unfinished Elizabethan building remains a mystery.

A science fiction-inspired apartment building designed by a famous Spanish architect.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

Three underground crypts and a pointed arch under the bell tower make this cathedral unique among Romanesque churches.

An ingenious solution to a tricky engineering problem, this spiraling bridge takes drivers for a dizzying spin.

This church looks more like a spaceship than a house of worship.

One of Amsterdam's narrowest houses is located right across the canal from its widest.

Skulls and skeletons are omnipresent in this church dedicated to souls trapped in purgatory.

This cliff-face port is considered a masterpiece of mining engineering.

An IT-specialist-turned-farmer reintroduces an Austrian food tradition while promoting snails as a sustainable "future food" option.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

A neo-Gothic mansion now houses a wunderkammer of analog tech that hits on all the senses.

Macabre museum devoted to historical Viennese murders.

Remnants of a Victorian garden feature sitting in public woodland.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

Hear the quietest sound from across the dome.

Plaques on its facade commemorate the Tiber's most destructive deluges.

This ancient Roman arch misled treasure hunters for centuries.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.