This mushroom-shaped rock has frustrated and fascinated locals for centuries.

Polish luminaries and masterful folk art find sanctuary in this unique cemetery.

An artificial hill and apparent calendric structure built in the Early Middle Ages immortalizes a legendary Polish princess.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

An open-air museum of 18th-century homes and churches transported from various villages in Southern Poland.

The hollow trunk of this 650-year-old tree was used as a hideout by two Jewish brothers during World War II.

The oldest funicular in Lithuania has been climbing this steep hill since 1931.

This magnificent Art Deco church is a reflection of Lithuania’s turbulent history.

Legend has it that not even Stalin could pull down the 2015 European Tree of the Year.

Two old windmills got a new life as oversized sculptures of a man and a woman.

These ancient monoliths make up one of the largest archaeological sites in Palau.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

This 13th century Gothic brick castle is the largest in the world by surface area.

Relics from an era long gone, sit idle outside this Estonian museum.

Abandoned Soviet base once stocked with short and medium range missiles pointed at western Europe.

For the last century, this international border within a small town has appeared and disappeared various times.

This ancient theater was once the home of fierce gladiatorial battles.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

This statue once earned the distinction as one of the "Three Major Disappointments of the World."

Constructed by forced laborers, this submarine pen is now a museum and war memorial.

The oldest continuously operating pharmacy in Europe.

A series of concentric circles represented a bold new experiment in socialist urban planning, and it notoriously difficult to get around.

This former medieval prison now unlocks Estonia’s rich photographic history.

One of the most well-preserved castles in Italy also contains a rare medieval example of a port fortification.