The new area is Enkanomlya, which exists underground and is entered via a deep pool in Inazuma.
you’re gonna wanna be adventure rank 30 to access it.
It’s a good example of what Genshin does well, wringing atmosphere out of relatively simple building blocks.

The whole of Enkanomlya seems coated in fog and lit in cool blues by glowing plants.
And of course there’s tall things to climb and leap off.
As a gacha game, the bigger new addition is arguably the new characters.

Or if you’re already playing the update, check out ourShenhe buildandYun Jin buildguides.
The RPS guides team doesn’t hang about.