“I suspect the culture is there but for the benefit of the locals, not the tourists”

That is the key point Gibraltar is a real place first, rather than a ‘destination’.

And for most tourist yes it is a single day / day-trip vist place, that is the ideal period of time for most of what is available for tourists on the surface.

[Caves, tunnels, upper rock (generally), seeing the airport - or staying low with a dolphin trip etc.]

Personally, I think you would really enjoy the Great Siege Tunnels (which it sounds like you missed) and the more recently opened WW2 tunnels (althoug only a small sections of the more than 30 miles of tunnels is open to the public).

Glad you enjouyed it anyway. It’s a real place.

There is more, but you need to change mode a bit. Certainly not tourist, but visitor….