Hidden in the background of the song "Adam's Apartment" used in that area, a quiet, distorted sample of dialogue spoken by actress Sean Young from the 1982 film "Blade Runner" can be heard, specifically the scene where Deckard meets Rachael after a replicant owl flies across the room and she asks him "Do you like our owl?"
Contributed by MehDeletingLater
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There is a Weighted Companion Cube from the game Portal hidden in Prague, inside the "Antiky" shop.
Contributed by Ang3lus033