What is Tirtha, and why is the area around it red?

[PortalBreaker]

I can't seem to understand what this area is.
It's covered in red, even though the radio tower covering it is overtaken, and the nearby enemy out posts have been taken care of.
There are no enemies close to it either.
And there's a safe house there, but I can't enter.

[Mang]

Tirtha is a little hub town that later gives you side quests as well. I also went there when the safehouse was still locked. It actually unlocks during one of the story missions, so keep playing them.