Military tunnels were first excavated in the cliffs in 1797 and 1802. These were converted and extended during World War II to house a naval operations center, coastal artillery, anti-aircraft operations and hospital. During that war, its facilities played a critical role in the Battle of Britain, as German and British aircraft fought above the cliffs. The cliffs become famous in America with the wartime song The White Cliffs of Dover.
Tours of the tunnels can be booked in Dover or in London, which is only two hours away.
• Rock of Gibraltar, United Kingdom: This rock is perhaps the most recognizable natural wonder in Europe.
For many Americans, it is the symbol of an insurance company. But for most observers, the Rock symbolizes steadfast toughness and might.
True to that role, Gibraltar has been a fortified bastion for centuries. Strategically located close to the entrance of the Mediterranean, the Rock is honeycombed with more than 30 miles of military tunnels. Some tunnels have cannons aiming out from windows in sheer cliffs, some lead to interior storerooms. Though it is connected to the Spanish coast by a tiny isthmus, Gibraltar has been a British Crown Colony since 1704 and remains so despite Spain’s efforts to annex it.
From land or from a passing cruise ship, the Rock is an impressive sight, its distinctive profile sticking out into the Mediterranean. Tour vans take visitors to explore some of the tunnels; on the way up they always make a stop so passengers can see Gibraltar’s tailless apes, Barbary macaques. At Europa Point, the Rock’s southernmost point, visitors brave strong winds to gaze at the mountains of Africa across the Straits.
Gibraltar has another attraction that has nothing to do with its status as a natural wonder: It is a duty-free oasis, one of only two in Europe, so, sadly, some visitors never explore further than the many shops that line Main Street.