Quote Originally Posted by waldronate View Post
In fantasy, physics need not apply. A DM I once knew decided that the big mountain in the center of the island should disappear, leaving a big hole. The large river that had flowed from the mountain to the sea now served as a channel for the sea to flow back into the big hole. Implausible, but possible. And certainly not stable. Ever since the big hole appeared just south of the Sea of Fallen Stars in the Forgotten Realms, I've been waiting for some enterprising gnomes to dig a canal from the sea to the hole and set up a few waterwheels on it. The unintended erosional consequences and migrations due to flooding would be hilarious!
So, pretty much this: Qattara Depression Project - Wikipedia, the free encyclopedia