9/11 changed architecture and urban design forever

In the UK we had the IRA bombings[0] up until the mid-1990s which changed architecture and urban design. If you worked in the financial district in London, for example, you would have had to pass through the "ring of steel"[1] to get to work, none of the buildings had large car parks underneath (that's one of the things that surprised me on my first visit to New York - some of the tall buildings had several floors of car parking underneath), the few vehicles which were allowed into the small car parks were always inspected carefully for bombs, building windows were shatterproof and offices typically had plans showing the red, amber and green zones for blast debris so seating could be arranged accordingly, all post was X-rayed coming into buildings (a colleague once inadvertently triggered an alert by having a plastic light gun for his Playstation delivered to his work address), etc. All before 2001.

[0] https://en.wikipedia.org/wiki/Provisional_Irish_Republican_A...

[1] https://en.wikipedia.org/wiki/Traffic_and_Environmental_Zone

the only 3 steel buildings ever to come down in complete free fall in a matter of seconds due to "fire"? NIST's explaination breaks the fundamental laws of physics

Remember when buildings complexes had multiple entrances ? It is increasingly rare nowadays. Using private but publicly accessible ground as thoroughfare is on the way out too. Fences go up everywhere - though 9/11 is only one part of that security paranoia... My apartment building in La Defense is the only one left on our street with a single layer of access control - two is most common and three is the standard nowadays (and when I was a child, in the early 80's, there was none and it was normal). I don't want my city to feel like a compartmented facility.