Not trying to hijack the thread, but I've gotten into 2 towers and 1 TRACON. I won't say the names of the airports, but I took a student to one tower and got in simply by pressing the buzz box and telling a controller who I was and why I was there. Following a quick scanning with their remote camera, I was in. The other was simply a phone call, which consisted of the guy telling me the parking lot gate access code and also mentioning that the security gate around the tower as well as the main entrance door to the facility was left open because he had an umbrella with him when it was pouring down rain and didn't want to put it down to close the gate.
The TRACON was a different story. When we pulled up, the guards did a complete search of my car and asked for my and my passenger's ID. They took it into their shack, after which I presume they did a background check (my passenger was a black guy from Jamaica...we were writing a report for our ATC class on the new STARS System, which this facility was equipped with).
I was kinda shocked about how easy it was to get into the 2 towers.