Glasgow Central railway station is a magnificent Victorian edifice that's still a busy working terminus, but it's underneath where things get really interesting. The hourly tour below Central gets very emotional and very political very quickly. There's the platform where the bodies of soldiers killed in the Great War were laid out for their loved ones to identify and claim. Then there's the ladies-only platform, established to protect women from the cutpurses and worse who lurked in the smoke-filled shadows. Head guide Paul Lyon discovered it when he knocked a hole in a wall that he felt was in the wrong place. His withering summary of the aftermath of the Great Train Robbery – the ill-fated mail train left from here – is worth the price of admission alone. Into this hour-long transport of delight are woven tales of the Highland Clearances, the Irish potato famine and the famous and infamous who passed through.
The tour costs £13 ($24); see glasgowcentraltours.co.uk
Vietnam is an absolute must for tunnel buffs, and the Cu Chi tunnels dug during the "American War" are on almost every package tour itinerary. There are two locations. At the busier Ben Dinh, the tunnels are narrower and more authentic; you might have to crawl through, but the bunkers – kitchen, armory, tailor and field hospital – are accessible from the surface. Nearby Ben Duoc has tourist-friendlier tunnels but they are the only way to get to the bunkers. Tunnels under the Reunification (former Presidential) Palace in central Saigon were the command HQ for US and allied forces, and there you can see the old war rooms complete with maps and banks of ancient telex machines and valve radios. At Vinh Moc, north of Hue, tunnels dug purely to protect locals in an underground village are large enough to walk around in – no crawling required. To learn how the Cu Chi Tunnels were first explored by Australians see tunnelrat.com.au
A half day tour by river of the Cu Chi Tunnels costs VDN1899 ($139) See lesrivesexperience.com
Trainspotters and tourists alike are drawn to the London Underground, but the movie Darkest Hour has increased the attraction of visiting the abandoned station that was Winston Churchill's bomb shelter during World War 2. Underneath Mayfair, between Hyde Park Corner and Green Park stations, Down Street was a working station for 25 years until 1932. Eight years later it would be reborn as Churchill's secret underground HQ during the worst days of the Blitz, when London was bombed every night for 57 days. Small group tours of Down Street take 90 minutes and sell out very quickly. London Transport Museum also hosts tours of several other historic, decommissioned stations and tunnels.
The tour costs £85 ($160); see ltmuseum.co.uk
You have to head underground again for the top tourist attraction in Newcastle, in the north of England. The Victoria Tunnel was originally built to transport coal 4 kilometres from the Town Moor to the River Tyne, where it could be loaded on to ships. Ingeniously, because the tunnel was on a gradient, full coal trucks could just roll down to the docks before being pulled up empty on a rope attached to a stationary steam engine near the pit head. Opened in 1842, the tunnel was only operational for 18 years, but during World War II it served as a mass air raid shelter and more recently 700 metres of it were opened to the public. One and two-hour tours, historic displays and informative guides have made this Tripadvisor's number one activity for Newcastle; advance bookings are essential.
The tour costs £8 ($15); see ouseburntrust.org.uk
During the 1970s, 20 years after the end of the Korean War, it was discovered that North Korea had been digging tunnels under the demilitarized zone (DMZ) separating them from the South. With the capacity to move 3000 troops an hour, plus field artillery, they were obviously intended to be deployed for a possible future invasion of the south, although the North Korea government insisted they were disused coalmines. Now tourists can visit three of the tunnels on guided tours and, for the equivalent of about $12, visitors can take a ride down 250 metres of the "Third Tunnel of Aggression," which reached as close as 40 kilometres to Seoul. There are a number of tours to the DMZ from Seoul, including one to Panmunjeon, scene of recent diplomatic encounters, where you can walk across a room and technically be in the North.
The tour costs from KRW38,000 ($48); see koreadmztour.net
You have to be physically fit and fairly mobile to join the tours underneath Fremantle Prison in WA. Once you're in your safety gear, you have to climb down 20 metres to explore a labyrinth of tunnels dug by prisoners as part of their hard labor sentences. For only $10, you'll be led through dry sections of the tunnels on foot, before boarding replica convict punts to explore the flooded passageways accessible only by boat. Did anyone ever use the tunnels to escape? You'll have to ask the guides.
The tour costs $65; see fremantleprison.com.au
Jimmy Thomson was a guest of People Make Glasgow and Radisson Red hotel.