It is the biggest known exporter of iron and steel to the Northern Kingdoms and Nilfgaard, and many mines, foundries, forges, etc. are located there. Mahakam iron is famous for its quality and is considered to be the best in the world. Aside from its iron, Mahakam is famous for its weapons, forged using advanced gnomish technology.
Mahakam is not visited in the game, though it is referred to then and again in discussions, books, and journal entries. dwarven spirit is allegedly made in Mahakam. There is also Mahakaman mead, which is regarded as "the dwarves' greatest contribution to world culture". Numerous weapons in the game, including light weapons, heavy weapons, and a sword, are of Mahakaman make.
During Act II, when you first bump into Iorveth, he mentions that Vernon Roche was responsible for the pacification of the hills. At the end of game, we can see what Zoltan mentioned in the novels: the Nilfgaardian army passing by without any attack.