There’s more to tunnels than meets the eye – and not just because they’re under cover! Here’s five questions about these engineering marvels.

1. From 1906 to 1982 the longest railway tunnel in the world was in the Alps. What is its name?
2. The Channel Tunnel incorporates the longest stretch of undersea tunnel in the world, at 37.9 km (23½ miles). What’s the average thickness of earth between it and the sea bed?
3. The three tunnels dug for the mass escape from German prisoner-of-war camp Stalag Luft III in March 1944 (The Great Escape) were called Tom, Dick and Harry. Which was actually used for the escape, and how long was it?
4. The Marmaray Tunnel opened this month, connecting Europe and Asia. Where?
5. The Umeda Exit of the Hanshin Expressway’s Ikeda Route in Osaka incorporates a short tunnel. Why is it unusual?

Check your answers here!