The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

The Great Fire of London and the regulation of one-way streets both started in this alley.

Legend has it this 11th-century castle was paid a visit from the devil.

A memorial to the nearly 10,000 American soldiers laid to rest on the beaches of Normandy during WWII.

A monument to the thousands of Canadian soldiers who died capturing the French ridge during World War I.

In the shadow of a former battleground, the resting place for nearly 2,000 soldiers who died in World War I.

This memorial museum chronicles the apocalyptic destruction of the First World War.

In an area where the remnants of WWI are discovered on a regular basis this preserved frontline trench may be the most amazing.

A moving memorial to the fallen and missing from WWI trenches.

The site where one of the most famous poems of World War I was composed is preserved to honor the legacy of the work.

A rare example of World War I trenches from the British front.

Near Belgrade, an ancient-looking sarcophagus serves as a World War I monument.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A pair of connected skyscrapers form this symbolic gateway.

The first mosque in the world to receive electricity.

A number of craters left by fatal mortar strikes have been filled with red resin to remember those lost during the Siege of Sarajevo.

Oriental bazaar in the heart of Sarajevo.

The place where World War I began.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

Bridge that died in war and was resurected.

This Croatian island is for sale but no one is buying due to the dozens of accused Nazi sympathizers who were massacred there after WWII.

The now-overgrown beach resort was once frequented by Yugoslav military elite.

The complex has been abandoned since the Croatian War of Independence, barring a stint as a set for 'Game of Thrones.'