Mega city 1

I'm lost for words to. A prison big enough for 40,000 inmates - that's a bigger population than some cities.

 

As someone with an interest in the martial arts, I know of a piece of history that demonstrates why this is a bad idea.

Anyone who might be interested might look up the history of the art of capoera. It's a Brazilian martial art disguised as a dance (a dance with kicks that when tested on modern day equipment, are more powerful than most other combat arts). In a nutshell, African slaves brought to Brazil developed it in secret. It's disguised as a dance so that if they were seen practicing the observer would just think it was some tribal dance routine. They then used it in an uprising, killing armed guards before they even realised they were under attack.