The clink of chains and the lash of the overseer's whip may have long since passed, but Australia's latest tourist attraction promises an insight into the hardships endured by thousands of convicts transported in the 19th century. A labyrinth of tunnels and wells beneath the colonial-era port town of Fremantle, in Western Australia, opened to visitors this month for the first time since they were hacked out of limestone rock by convict labour 150 years ago. The tunnels lie directly beneath Fremantle jail, and were dug from the 1850s onwards to provide the prison with a steady water supply. Western Australia was the last Australian state to end the transport of convicts. More than 10,000 British and Irish convicts arrived between 1850 and 1868. The job of excavating the tunnels was assigned to the most recalcitrant prisoners, who toiled underground in shackles and with 23kg lead weights attached to their waists to prevent escape. At least one man is known to have died from exhaustion, and several collapsed as they stood in waist-deep water working manual pumps. Tourists wear waterproof overalls, boots and hard hats to explore the tunnels, descending about 20 metres underground by a series of ladders. The first part of the 21/2-hour tour takes them along a 400-metre dry stretch of tunnel. The next 500-metre section, however, is flooded, and tourists have to take to specially made boats, replicas of those used in the 1920s for maintenance work. The passageways, 2.5 metres high and 1.5 metres wide, still bear the marks of the pick-axes that were used to excavate them. 'We call it extreme heritage tourism,' said Graeme Gammie, executive manager of the prison.