This irregularly shaped sea fortress has defended not one but three different sovereign states.

Estonia's largest creative city is a vibrant bohemian hub located within a former industrial complex.

An empty relic of the Moscow Olympics crumbles away in Estonia's capital.

An underground nightclub helped spark a "Singing Revolution."

This free museum is building a collection of books that are banned, censored or burnt around the world.

A secluded art gallery hidden within the cellars beneath Tallinn’s medieval monastery.

"There's nothing there," and other lies the KGB told us.

Freddie Mercury's childhood home is now a monument to the iconic Queen rockstar.

Uganda's smallest savannah park is home to over 350 species of birds and mammals.

The world's only facility where orphaned mountain gorillas are cared for.

Mount Nyiragongo has erupted at least 34 times since 1882 and is home to the world's largest lava lake.

Burial site of the world's most widely known researcher on the endangered mountain gorilla.

This massive underground salt mine now holds a sci-fi theme park in its depths.

A stunning 18th century pharmacy and medieval chemist's collection.

Packed to the ceiling with antique taxidermy and hunting arms.

The ancient Greek Titan guards this massive dam holding a lightning bolt to symbolize electricity.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

Climbing to the top of the cathedral's bell tower offers sweeping views of these medieval ruins.

A fire once nearly devoured this gorgeous 14th-century Gothic cathedral.

This snug medieval lane is one of the narrowest streets in the world.

No one knows who built this strange cave of worship or exactly why.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

This enormous abandoned prison was once dubbed the "Bastille of Romania."