The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

A historic cavernous cistern lies hidden behind a wall at San Marino’s stamp and coin museum.

The San Marino-Rimini railroad was short-lived but this tunnel once provided shelter for hundreds of refugees during World War II.

A model village fit for an emperor.

One of the world's tallest statues is also one of its most hated.

Church built on the site where the last tsar of Russia and his family were killed.

Hidden in a metro shop under a shopping mall, this small museum tells the story of one of the world's largest urban transit systems.

This frozen-in-time summer home outside Moscow provides a look at Russian life in the 1950s.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

Former headquarters of the KGB.

The oldest museum in Russia is home to a fascinating collection of nearly two million anthropological artifacts and anatomical curiosities.

Stunning examples of Russia's 18th-century wooden architecture.

This Russian religious complex is a Frankenstein's chapel that includes influence from almost all the major faiths.

Palace where the nearly un-killable Rasputin was murdered.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

Moscow's other, lesser known kremlin is a fairytale-like cultural complex modeled after Old Russia.

These 400-year-old ruins are all that's left of the monastery where Ines de Castro was assassinated by the King of Portugal.

An unassuming music museum recounts the rags to riches story of a dramatic Portuguese genre.

A micronation on an islet along the coast of a Portuguese island.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

A lush oasis full of vibrant plants and striking geometric displays.

One of the largest Roman settlements in Portugal.

Local lore says the devil built this beautiful medieval bridge to help a fleeing bandit.