The first episode that shows the alternate-universe Dream World tower is not clearly identifiable from the search results I found , so I can’t confirm it with confidence. The closest match I found was a discussion noting that alternate worlds are hinted at in the first episode, but it does not specifically verify the tower scene.

What I could verify

  • A forum post about Dark says alternate worlds were hinted at in the first episode.
  • I did not find a source in the available results that definitively names the first episode showing the alternate-universe Dream World tower.

Best match

If you mean the Dark universe and the alternate-world tower imagery, the safest answer is that it is introduced as a concept very early, but I can’t confirm the exact first episode for the tower itself from the available evidence.

TL;DR

  • Confirmed: alternate worlds are hinted at in episode 1.
  • Not confirmed: the exact first episode where the alternate-universe Dream World tower appears.