This small 16th-century church in Athens is almost entirely surrounded by a modern building.

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

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

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

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

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

This colorful statue welcomes visitors to a Barcelona park.

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

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

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

One of Antoni Gaudí's least-visited works, an homage to Catalan patrimony that mixes neo-Gothic with Modernista forms.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.

Religious dwelling in a Spanish volcano.

Possibly the oldest church in Barcelona, this basilica has its pagan and Christian mythologies all mixed up.

A beautiful but toxic fountain of mercury.

The unexpectedly beloved remnants of a controversial thermal power plant.

Mountain where Jesus was first tempted by the Devil.

Of course Salvador Dalí lived in a castle...

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

Week-long block party becomes a competition for the best decorated street.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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