Driving along I noticed a facility with a lot of interesting pipes and valves and a very imposing gate festooned with severe no entry, no trespassing signs and warnings of danger:
Looks nice and secure right?
Let's zoom out a tad.
As you can see, the fence does not enclose the facility and you can even fit your car or truck around the gate and get to all those interesting looking valves and such. Basically the gate and warning signs will only keep out those who don't want to get in, as anyone who wants can get in with no effort at all.
Borepatch's often quoted statement that security wasn't an afterthought, it wasn't thought of at all seems to apply, and not just to cyber-infrastructure but to the physical. If you're not reading Borepatch regularly, you should.