There is a cavern complex in the hills to the north of the great kingdom that is easy to find.  And inside this cavern complex are several pathways down, leading into the underdark, the miles and miles of caves, caverns, and excavations that led down to various underdark routes, going between layers of soil and rock to touch on the cities of underdark beings.<br/><br/>At the surface it only appears to be a cave, but enter it and discover that it's no ordinary cave.  Wall markings would lead on to Ringin's Tavern, a place of underdark truce, where all sorts could meet and mingle.  Though, from Ringin's a clearing lead to several paths down further into the underdark, the paths diverging and never re-connecting, going deeper and deeper...<br/><br/>