AS PART OF THE continuing onslaught against militants in Gaza, the Israeli Defense Forces are targetting not just enemy guerrillas, but the vast network of tunnels that snake beneath the embattled Mid East territory. For years, insurgents have used the labyrinth of passageways to smuggle food, supplies and armaments into Gaza as well as to launch raids into the Jewish state. The use of tunnels is hardly a recent development in warfare. In fact, armies have been burrowing beneath the battlefield since ancient times. In many cases, these excavations survived the ages and are open to tourists and historians alike. Here are some notable examples of wartime tunnels that can still be visited today:

In the 6^th Century BCE, the ruler of the Greek city-state of Samos, Polycrates, ordered his military engineers to construct a one-kilometer underground causewaybeneath his own fortifications. The passageway, which ran from inside the settlement and through the base of nearby Mount Kastro, wasn’t dug to move soldiers, but to keep the city supplied with fresh water in the event of a long siege — the narrow shaft led out to a natural spring. Although details of the tunnel, one of the first ever to be excavated from both ends simultaneously, was recorded by the ancient historian Herodotus, its precise location of was a mystery to archeologists until 1882. It’s now a popular tourist attraction.

Many of the hundreds of saps burrowed out by the British, French and Germans beneath No Man’s Land during the First World War were packed with high explosives and then detonated. In some cases, these mines and their resulting blasts were so gigantic, the ground shook as far away as Dublin. Yet not all of these subterranean causeways were obliterated. As reported on MHN in 2012, archeologists have been mapping a series of intricate dugouts that were carved into a limestone quarry at Confrécourt, about 50 kilometers northeast of Paris. In fact, the French countryside is pocked with hundreds of these complexes along the old Western Front, almost all of which feature elaborate carvings and ‘cave art’ created by the soldiers who inhabited the spaces nearly a century ago. American photographer Jeff Gusky recently showcased many of these locations and their lost artistic artifacts in a lavish photo spread that’s about to be published in National Geographic magazine. Watch for it in August.

Beneath the sprawling expanse of Dover Castle on England’s Channel coast, lies more than five kilometers (three miles) of tunnels dug into the loose chalk of the famous White Cliffs. Although the fortress itself was built in the 12^th Century to protect the British Isles from French invasion, the passageways weren’t fully expanded until the Second World War. While initially serving as bomb-shelters, in 1940, the military used the caverns to coordinate the massive evacuation of more than 300,000 British soldiers from Dunkirk. The complex, which housed a field hospital as well as a movie theatre, was also one of the communications nerve centers of the epic disinformation campaign leading up to D-Day aimed at fooling Hitler into believing that the Allied invasion of France would strike at Calais instead of Normandy more than 300 km to the east. PREVIEW: MilitaryHistoryNow.com will be visiting the tunnels of Dover next week, among other locations, as part of a wider tour of southern England. Stay tuned for pics and video.

More than 1,700 km (1,000 miles) to the south of Dover, there exists another even larger maze of British tunnels — Gibraltar. Almost as soon as England seized the territory during the War of Spanish Succession, military engineers began converting the 1,300-foot tall mountain, known as “the Rock” into a veritable anthill of shafts, passageways and dugouts. Over the next 200 years, more than 11 kilometres (seven miles) of passages were hollowed out. During the early months of the Second World War, the British army carved another 25 kilometres (18 miles) in anticipation of a Nazi invasion of the strategically vital naval port. Military intelligence even planned on sealing agents equipped with supplies and radios into the mountain in the event the territory fell to the Axis. Today, the tunnels are a popular draw for tourists.

Japan’s own ‘Rock of Gibraltar’, Mount Suribachi on Iwo Jima is also the site of a vast system of underground corridors, bunkers and concrete reinforced gun emplacements, all of which were cut right into the volcanic rock. A quarter of the island’s 22,000 defenders spent much of 1944 blasting and burrowing their way into the 550-foot (170 meter) mountain that overlooks the island. More than 70,000 U.S. Marines stormed Iwo Jima in February of 1945. It took the Americans a month to clear the defenders out of the 18 kilometres (11 miles) of passageways – all but a few hundred of the Japanese on the island were wiped out before the fighting subsided. Some of the Iwo Jima tunnels survive to this day and can still be visited.

One of the Cold War’s most secret tunnels only recently became a tourist attraction. In 1954, British and American intelligence agencies in West Berlin secretly burrowed under the Soviet sector of the city and tapped into phone cables connected to Moscow. The 500-meter (1,500 foot) shaft took more than a year to complete. During the course of the program, dubbed Operation Gold, western spy agencies listened in on 400,000 telephone calls and recorded 6 million hours of conversations. It all came to an end in 1956 when an East Berlin road crew unearthed the tunnel while doing routine maintenance. Amazingly, the Soviets actually knew about the phone taps by way of a highly placed mole in NATO, but were loathe to act too swiftly on the revelation for fear that it might expose their agent in the west. A segment of the Operation Gold tunnel has been on exhibit at the Allied Museum in Berlin.

The U.S. and Britain weren’t the only cold warriors to tunnel into the earth. During the conflict in Southeast Asia, Viet Cong insurgents built a veritable city beneath the streets of Saigon from which they waged an unrelenting guerrilla war against South Vietnam. Today, one of the country’s most popular tourist attractions, the staggering 120-km (75 mile) warren known as the Cu Chi Tunnels, includes restored living quarters, field hospitals, storage depots and command centers. Another similar but smaller complex near the former border between the north and south also draws visitors. The Vịnh Mốc complex sits 100 feet beneath the DMZ and was a conduit for communist infiltrators and war materiel, as well as a shelter for up to 60 families that were hoping to escape the ravages of bombing on the surface.

The outskirts of Seoul, South Korea is the site of another once-secret sap that’s now open to the public. Known as the “Third Tunnel of Aggression”, the six-foot-wide passageway runs at a depth of nearly 75 meters (250 feet) from the North Korean side of the Demilitarized Zone (DMZ) more than a mile (1.7 kilometres) into South Korea. Discovered following a tip from a defector, it was one of several tunnels secretly dug by the reclusive Pyongyang regime after the 1953 ceasefire. The conduits were designed to be used by communist forces in the event of a repeat invasion of the south. Four of the passageways have been found; authorities suspect there are dozens remaining. As many as 30,000 troops would be able to pass through each tunnel per hour if necessary. South Korean forces sealed the shaft with concrete, but allow tourists to access portions of it.

Sadly, no one can visit the tunnel beneath a Civil War-era stronghold in the New York burrow of Queens known as Fort Totten – that’s because it hasn’t been discovered yet. But many locals and some historians steadfastly maintain that a secret passageway does in fact exist and connects the 150-year-old bastion with Fort Schuyler in the Bronx more than one kilometer away (.6 miles). The tunnel would have had to have been dug beneath the East River at a depth of more than 100 feet — an astounding engineering feat in the 19^th Century. Both outposts were designed to protect the approaches to New York City from Confederate raiders. Despite skeptics who claim there would have been no need to link the two forts using an underground (and underwater) conduit, some historians continue to scour the grounds of both locations for any trace of the sealed openings to the mysterious passage.