Anybody knows what is this place?? (South of the Arena)

https://preview.redd.it/jcm1k7bhvnfh1.png?width=1920&format=png&auto=webp&s=6f86a8df3991a88e79685b1f9bd30d98e73f10f2

https://preview.redd.it/u9551zynvnfh1.png?width=1920&format=png&auto=webp&s=f38c57345ec94d7f6313cda346faf1a478acbac5

I was exploring again on this game and it seems like a large portion of the south is explorable and jumped here (got stuck unfortunately) theres some enemies downthere too, but i dont know how to get there. Is this the DLC or maybe something i dont know?