Our guide (Chris) has been associated with the excavation of the tunnels for years and so was able to talk very personally about how they cleared them, discovered new twists and turns, found hidden treasures and so on. Having dodgy knees I was a little concerned about the number of steps but it was all fine - you can take your time, you don't do them all at once and there are handrails everywhere. I thought it might feel a bit claustophobic but the chambers are very large so I didn't get that feeling at all. We all looked great in our hard hats and high-vis jackets too!