I found three nests inside the lair, and three while going down/up to quarry. However, I am missing one more. Where can the last one be found?
Harpy’s Nests located
the-witcher-2
Related Solutions
From the manual:
4.3 Development paths
Training – the primary development path. To begin another path, you must spend at least six talents on the talent path abilities..
You find out the way to destroy the Nekker nests by obtaining enough knowledge about the Nekkers, either by reading a book about them (available in Flotsam) or by fighting them. If you're at knowledge level 3/3 (character screen -> Attributes -> Knowledge) there will be the following text about the Nekkers
Witchers can user their full range of skills and techniques when fighting nekkers. Signs, bombs, poisons and oils that augment bleeding are all extremely effective against the beasts. Nekker nests are best destroyed with Grapeshot bombs.
To build a Grapeshot bomb you first need the schematic, which is available from the elf Cedric. Just look out for the craftsman icon on the map in Lebinden to find him. After you bought the schematic you need to meditate and then build some Grapeshot bombs:
Best Answer
It turns out that the best way to get the 4 harpy nests is to go down to the quarry, not up. This is because if you go up, there's one battle where you will lure two groups of harpy, one group for each nest.
I was going up, so I ran into two groups, but didn't deduce that the other group belongs to another nest.
The group which I've missed is next to the burnt house at the top of the quarry.