Yuri_G, it's easy to find even without a screenshot if you know there's a path. I found this path after taking the Castle – I just explored all the passages. One of them led to the mages' treasure. At first, I was happy – I thought I had found another one. But if you want, I can send it to you tomorrow, as my lunch break is over today. Where should I send it?...
Post it in this thread. Others might find it interesting too. And send me a message privately.