Hi Rand
and welcome to the Ironworks forums!
Asking a question after having tried yourself isn't really cheating, you know, and even if it is, as long as you enjoy the game, who cares? [img]smile.gif[/img]
Anyway, in answer to your question: The Hammer of Thunderbolts is located in the Sewers under the Temple District of Athkatla. There are two secret doors there, and you need to go through the right-hand one.
However, it will be locked and to open it you need a key you will find in the Windspear Hills (I don't know if you already went there, so I won't say anything more so I won't spoil it for you). SO if you haven't done the Windspear Hills quests yet, do so now. The key you need is called "Sewer Key".
Leuk trouwens, nog een Nederlander!