Take a tour of Spinalonga Fortress in Crete, Greece - part of the World's Greatest Attractions travel video series by GeoBeats.

Just off the coast of the famous Greek island of Crete is a tiny island that is popularly called Spinalonga.

On this island is a centuries-old fortress that has been built into the rock itself.

Spinalonga Fortress was constructed here in the sixteenth century on top of the ruins of an ancient acropolis.

The thick stone walls and sturdy construction quickly make it obvious how this fort has remained here for centuries.

Because of its design and position, the Spinalonga Fortress was one of the most important fortifications in this part of the Mediterranean.

Visitors can reach the fort by a daily boat for a day-long tour of the island.