Batman Arkham Knight: Guide to the Watchtowers, Gotham Gates
Let's see how to complete one of the game's side quests.How to destroy all militia watchtowers
"Occupy Gotham" is one of the "wanted" side missions of Batman Arkham Knight which, among other things, is also part of the Deathstroke questline.
In this mission it is necessary find and destroy the 21 militia watchtowers, the first you will take out as part of a mission of the main story, then the secondary quest will be activated where you will have to find and destroy the remaining 20.
The video you can see above shows where all the watchtowers are located on each island.
Destroying all the watchtowers will complete the "Occupy Gotham" mission and also unlock the "Gotham Gates" Trophy / Achievement.