The first is in the spider cellar, the second is the little door in Brekk's armory.
That's all for a good portion of the game...
After completing Shiverbane and defeating Maulgak and opening the Eye Gate next to his arena, you have the option of flying thru the Eye to Surdana. When you go to the castle to get further guidance, you find the aftermath of a failed assassination attempt on the Lady Myschala's life, and are sent on a quick exploratory mission through a secret bookcase/entryway located behind Zola Dane's desk.
After a few turns, you'll find a wall that has slightly different brickwork than the rest, marking it as a breakable wall. Burst thru and pull the final lever, then proceed deeper into the hideaway to find an inactive portal.
Rynn prompts you to return to the general, where a cutscene happens pitting you briefly against Zola Dane, who has magically bound Lady Myschala.
After the battle, Zola flees and the cutscene shortly ends.
Now the payoff.
Go back down the stairs to the room where Gen. Dehrimon is standing and turn right. You'll see a wooden door. Go thru it and open the first door on your right, and you'll find around ten treasure chests, each containing largish amounts of gold.
The haul is around ten thousand gold, which isn't so impressive by this point in the game... but there it is.
Spend with fun and malice in mind!