Too late, you figure out that it is not just a doorway but some kind
of space/time vortex (excuse my Star Trek-like wording). A sudden
memory comes to mind (the first one since you woke up) - the time that
your Aunt's village was caught in a tornado while you were visiting.
You were lucky, landing in a bush extremely dizzy and battered, but
alive. Your Aunt was not. You push the memories aside and focus on the
here and the now.
That wasn't very smart. You're dizzier now than you were then, AND you
have no idea who or where you are, AND you don't know where or when
you're going, AND you're landing very hard on a rock outcropping and
in pain.
You suddenly realize that this must be that other world you just
entered. Then came your second memory - that you came to that city in
the first world for a quest.
You step into the doorway of night. You are definitely unprepared for
desert travel.