The Passage is a tunnel, artificially constructed to resemble the vaguest approximation of a natural formation, that leads between the dimensions, piercing the veil between the Prime and the Feywild. Walking from one end to the other will takes an hour, while strung along its length are numerous caverns—only in the loosest sense of the word—filled with clearly unnatural formations, the purpose of which can only be guessed at. In the center is the largest of these caverns, and the only one to lack any form of ornamentation.
It is unknown who created the Passage, but rumors persist that those responsible for the Finding encountered spirits that assumed familiar forms and spoke with them. Those same rumors claim that it is these spirits who created the Passage, although what design they were fulfilling with its creation is not readily apparent. In the months since the Finding, these spirits have not been seen by anyone using the Passage, so these rumors go unsubstantiated, although that in no way diminishes the power they wield over the populace.
All efforts that have been made to determine the Passages origin, through arcane, divine and psionic means, have failed. Whatever, or whoever, it is that built the Passage went to great lengths to make sure that no manner of probing can reveal its secrets. Even physical assault against the tunnel walls is repelled, causing more damage to the implement used than the cavern walls.
The lack of understanding has not dampened the usage that the Passage has seen since the Finding. Quite the contrary, in fact, as more and more people use it to travel between worlds everyday. The unfettered access to the host of unique natural resources and cultures found just on the other side has lead to a boon in trade that is in the process of bringing great wealth to Cormanthyr, even while the existence of such a thing so close to the capital gives the Coronal pause, do to the unknown military applications that it provides to any unknown adversary that may lurk hidden safely upon the other side.