Abandoned Mines, located just NW of Arwic, is also known as Subway, Sub, or Hub, depending on which server you play on. It is one of several Portal Nexus Dungeons.
At the bottom of the dungeon are portals to the following locations:
Qalaba'r, Mayoi, Hebian-To, Shoushi, Cragstone, Arwic, Holtburg, Glendon Wood, Rithwic, Zaikhal, Samsur, and Yaraq.
The Surface portal exit is just NW of Arwic.