M'Jinn was once the second biggest city in the world during the Age of Legends.
It was techonolgically advanced, with glittering skyscrapers, and yet not-so-advanced in that it was still lush, too, with greenery and parks. However, this presumably beautiful city was destroyed during either the War of Power or the Breaking of the World, and nothing save a few scraps of written knowledge remains to this day. The only known scrap gleaned from the destruction was that Eval Ramman, now known as Balthamel, once occupied a high position at an institute of higher learning.
The city was mentioned a few times during Graendal's and Sammael's secret meetings.
Sammael comments how Graendal's mood is as changeable as the weather in M'Jinn. Jordan could have written this as a reference to Michigan, where the weather is known to be sunny at one moment and rainy the next.