The main thing to know is you can access the ground floor lobby after finishing up as a corpo, but getting anywhere interesting needs either story progression or some creative thinking. Guards will definitely stop you from wandering into the secure areas though youll get proper access during certain mission endings and that new tower conclusion from the latest expansion.

Something interesting for the explorers out there - if youre determined enough you can actually use double-jump cyberware and air dashing to get past some barriers, which lets you peek at some pretty cool unused areas like different versions of saburos office and those underground netrunning floors. Just keep in mind this isnt exactly playing by the rules, and some areas might look a bit unfinished since they werent meant to be seen. The recent v2.0 update did add some nice touches to restricted zones though, especially around that jungle area and the executive levels up top, so theres definitely more to see now than there used to be.