What is this red area near Saint Denis?

2nd playthrough, it’s been a good few years but I don’t think I’ve noticed this before? It doesn’t say I’m wanted so I’m guessing it’s a hostile area but does anyone know what’s actually over there? Wasn’t sure if I could get there due to the river and I don’t want to go there just to instantly die 😂

2nd playthrough, it’s been a good few years but I don’t think I’ve noticed this before? It doesn’t say I’m wanted so I’m guessing it’s a hostile area but does anyone know what’s actually over there? Wasn’t sure if I could get there due to the river and I don’t want to go there just to instantly die 😂