These incredible tunnels were originally carved out by the Romans but in more recent times were used by residents of Maastricht as shelter during the Second World War. Utterly haunting tours, run by the outfit Maastricht Underground, take you deep into the recesses here while providing an excellent overview of the area’s history. It’s especially startling and moving to see the works of art, maps and even business advertisements created here by ordinary people trying to get by in the worst of times. Don’t miss this one, it will stick with you for a long while..