Area B-1 (Tomb of the Fallen).
The entrance from the south-east text describes "A strange and foreboding portal bars your way." However, the tomb map illustrates that entrance as a twisting hall opening directly into the tomb.
Running this game tonight (very fun!) I made the mistake of revealing the burial bier to the players based on the map, and then started into the flavor text, which I hadn't adequately grokked in advance, as I thought that the "portal" description must apply to the other entrance, which has a sort-of-portal on the map. Not the case I guess.