So just bringing it up again. I remember the last time some one asked. Still it's there......None what so ever and questions about it have been asked for a couple of years now.
But the entrance is still inviting. Surely it would be something to add "spice" to the game. Every city has one. Maybe a doorway to your city in another world. Maybe no more than one unit a day otherwise abuse potential. or maybe an alternative guild expedition.I have even seen ideas to give it some use. In the end, I think it is just decoration.
It is a weyrhold -- just waiting for some dragonriders to come along and Impress the dragons therein.
That would be a movie !Props for the Dragonriders of Pern reference! Still waiting for somebody to make that movie...