There are lots of interesting places to find, with nice loot sometimes. I've been hunting down question marks on the map, but I noticed that I don't have all of the places marked on my map yet for some reason.
I just destroyed a monster nest that was marked with a question mark, and found another one close by that wasn't marked on my map.
I know that reading the notice board can make places on the map, and I've read them all. But what can I do apart from that to mark all the interesting places on the map?