As mentioned we took a tour to the Cu Chi Tunnels. These are remaining tunnels from the Vietnam war.
Original entrance to a tunnel
Tourist entrace to a tunnel
At first I was not even sure if I could go inside once I saw how small the tunnels really are. But then I saw that the tunnel was very short indeed and just followed the group. We saw three tunnels.
I think this is a must for everyone visiting here. You have to see it and walk through the tunnels yourself. There is no description that comes close to the experience.