This is a very interesting tour, you walk from the tour meeting place to the cave entrance, takes about 10 min. Then you walk into the caves and wow, what and extensive labryinth of underground tunnels. They date back quite far when sandstone was quarried from the hills for the building of the Roman settlement. You can see the distince layers as the stone was taken out over the years. We learned that there was a complete set-up for evacuation of the city of Maastricht in case it was needed during WWII, complete with a church area including the stations of the cross, and a bakery! It was never needed to the extent it was set up but so interesting to learn about. It's quite a bit cooler than the air temp outside so bring a light jacket or sweater. We combined this tour with a boat tour, the boat mainly being the means to get to the cave area. Pretty and relaxing on the boat but that part could have been a bit longer in my opinion. You can get food/drinks on the boat but if you do order as soon as you get on or you won't have time to drink or eat!! I think it's about 15 min. each way on the boat. Overall, definitely worth a few hours of your day!