Vesper bar is a cute pretty chill bar sitting right next to the Cosmopolitan front desk.
I've been here a couple of times and have had a few of the specialty cocktails. They were pretty on point. Quite tasty and balanced.
The service is pretty good. The bartenders are friendly but not too friendly and I really appreciate that. When I'm alone at a bar playing on my phone I want to be left alone. Lol.
Obviously the cocktails are quite expensive but this is Vegas so I wouldn't expect any less.