[TuNiSiAnO1]

What is the best way to know that

[Hreesang]

Use your search button, bro, you will find lot of helps.
But okay, no problem, here is a Filterscript, try to learn something from the Filterscript:
https://sampforum.blast.hk/showthread.php?tid=161741

[denNorske]

Create approximate areas by using coordinates and perhaps Incognito's Streamer Plugin to define dynamic areas (or make your own function, works too) - then create a logic that parses the coordinates of the player and compares them to the values in the areas you've created. Name the areas and so on - that I would say is a simple way.

You can even make it simpler by creating squares/rectangles if you want, but that will also decrease accuracy in the city borders.