The Drunken Lizard Pub

How do I get to the land area towards the bottom left hand side of this map?

I can see enemies on the other side (killed a few with magic), but there seems to be no way to cross the big river

BOOOOOOOOM goes the barrel.
look for a weak wall along the corridor just north of the spot you can't get to.

I'm quite confused.

Are you saying there is a second entrance into the Northern Farrock Range, from the Farrock caves?

I am exiting Farrock caves, into NFR above the river.

In Farrock caves, I can double back, I've found the wall I can blow up. I go into it, it takes me back to the water area, and now I'm on the other side of the river. However from that side of the river, as far as I can see there is no way to actually exist Farrock caves and go into NFR.

edit: are there more than one blow-up-able walls in farrock caves?

Oh, I thought you were asking how to get to that spot.
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The answer is no: there is no exit (there) to south of river.
See: viewtopic.php?p=29302#p29302
(note that exit B is initially only available from the outside - until you go in there and flip the lever connecting that tunnel to the A-C tunnel)

When you got east of Eastwillow to Ruel's house there is a path to the northeast. Continue that way out of the zone and there is an entrance to the Farrock Caves near a monolith (quick travel marker). Then head east and you should be where you want to go. Have fun looting.