In Batter Call Saul, season 6, we have seen multiple times that there is an underground tunnel between Gus Fring's personal residence and the house opposite to his house across the road.
The two houses are in a really good and quiet neighbourhood.
I can only assume digging a tunnel is not legal, letting alone the tunnel is very well constructed with concrete reinforcement and etc. How realistic is it for Gus to pull it off in a quiet neighbourhood like his?