2. Château Gaillard

Towering above the River Seine, Chateau Gaillard was built by King Richard I to assert England's authority over his French holdings. Its multiple walls, deep moats and ingenious geometry were designed to terrify any foe. In 1203, a French king and his massive army lays siege, determined to push the English from the continent.

3. Dover Castle

High atop the white cliffs of southern England, Dover Castle was built by King Henry II to protect an empire. Its deadly gatehouses, layers of walls, and magnificent keep were engineered to crush the enemy. In 1216, an ambitious French prince and his determined troops descend to capture this key to England and with it, the English crown.

4. Conwy Castle

Positioned the wilds of northern Wales, Conwy Castle was one of several strongholds raised by King Edward I to rule over the Welsh. Its mighty towers, elongated arrow slits and majestic water gate were built to intimidate. In 1294, a rebel force arrives to put the king's castles, and English domination, to the ultimate test.

5. Malbork Castle

Stretched along the bank of the River Nogat in modern-day Poland, Malbork Castle was built by an elite group knights during the Baltic Crusades. Its distinct brick architecture, soaring walls, and deadly battlements were built to intimidate the local population. In 1410, a pagan-turned-king marches on the castle, determined to put an end to the Teutonic Order's reign.

6. Malaga

Located high above the Mediterranean coast, Gibralfaro Castle and its surrounding defenses are the monuments of a Muslim dynasty. Its daunting towers, brilliant water-storage, and one-of-a-kind passageway were engineered to withstand the most ambitious attacker. In 1487, King Ferdinand and Queen Isabella descend to capture this city and destroy the legacy it represents.