Italian cave with exceptional acoustics and an unsavory history.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

This massive blockhead sculpture hides an entire library.

150 or so scrounged-up lamps, chandeliers, and lanterns light up this alley in central Athens.

A tiny Greek Orthodox church from the Ottoman era hides on a busy city street.

These caves secretly held national treasures during World War II.

Legend says this sacred tree was a gift from goddess Athena.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

An ancient octagonal weather station named for the eight Greek gods of wind.

One of Antoni Gaudí’s earliest buildings, built between 1886 and 1890 for the industrialist Eusebi Güell.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

An early 20th-century bullring converted into a modern shopping center.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

Turntable anonymously received orphans, alms, and groceries.

This cafe offers a curated collection of treats and tipples made by monks and nuns.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

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

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

As its grandiose name implies, this wooden dome is unsurpassed in size.

This quirky roadside attraction provides insight into Minnesota's logging history.