Board Thread:Spoilers!/@comment-1916997-20160310013919/@comment-24674051-20160315165529

The door is of the same architecture that the Apprentice used to send Ingrid to the LWM, and to bring Isaac to the EF. It is also similar to the portal door that Rumple found in the abandoned Mansion. So while it may not necessarily be the portal to the EF (though I suspect it is), it definitely strikes me as a portal door.