The Yawning Portal

Once the site of the long-vanished tower of Halaster Blackcloak, the Yawning Portal's singular feature is the massive, forty-foot across well that descends some one hundred and forty feet into the first level of Undermountain. Other than this, the Yawning Portal is a dingy wooden tavern/inn frequented by adventurers and those who're interested in such. The rooms are usually let to adventurers, and similar folk.

It costs 1gp to head down the well, and another to get hauled back up. Torches provide light for the first fifty feet or so down before adventurers are swallowed by the darkness of Undermountain. The faint light can be seen at the top of the well from the room at the bottom of it.

While a lowering into the depths is cause for celebration, there is a heart-stopping moment when the bell rings from below, signaling that someone—or something—wishes to be let up. As there's no way of knowing exactly who or what is down there, everyone waits with bated breath to see exactly what rises up out of the darkness.