One of the largest caves in the world open to the public.

An ancient artistic garden parlor full of hidden water wonders.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

This basilica is dedicated to two saints, one of which is known more for his famous quote.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.

A local student's chance encounter with Keith Haring led to the creation of one of Europe's largest murals.

This medieval city gate is now a blend of the past and the modern world.

The “Sistine Chapel” of the Middle Ages merges 11th-century science and religion in wondrous hues.

The disputed geographic center, or "navel," of Italy.

This ancient Roman bridge was a key feature of the ancient Via Salaria road.

This Roman theater was crafted into the local tuff rock and was rediscovered during the 19th-century.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Museum dedicated to the terror regimes of Hungary.

Memorials at a Florence railway station remember the citizens who were deported from Italy and sent to extermination camps.

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

A lavish 16th-century mansion filled with spectacular staircases, fantastic frescoes, and gorgeous gardens.