It's hard to find them now with all the AI slop being propped up but the best search terms may be "Iranian tunnel bunkers full of missiles". It is mostly YT channels run out of India. The oldest video I have seen was from CNN ten years ago. Iran will occasionally let journalists see their latest tunnel.
This is a short one showing the 2nd to last generation of tunnels. [1] The latest tunnels are painted white including some that are under water. The older tunnels are not painted and one can see what appears to be reinforced concrete. When completed every tunnel is lined on both sides with missiles. This one [2] shows a couple generations of the tunnels. Found the old CNN video. [3]
This is a short one showing the 2nd to last generation of tunnels. [1] The latest tunnels are painted white including some that are under water. The older tunnels are not painted and one can see what appears to be reinforced concrete. When completed every tunnel is lined on both sides with missiles. This one [2] shows a couple generations of the tunnels. Found the old CNN video. [3]
[1] - https://www.youtube.com/watch?v=6YQ1R7ZAKxE [video][1m]
[2] - https://www.youtube.com/watch?v=MQtSPFrnKvo [video][5m25s]
[3] - https://www.youtube.com/watch?v=7_Gu_TjmV0E [video][2m12s]