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The room where Zuo Jun was located was inside a "mezzanine" of the Dubhe Tower. From the outside, it didn't look like there was a room there at all; the space was completely sealed off, with no passages connecting it to the outside world.
According to the design plans of the Dubhe Tower, this should have been part of the tower's load-bearing structure. If it were to be hollowed out, it would significantly weaken the stability of the building. However, this was only the conclusion from the perspective of ordinary people's understanding of architecture and material science. For the Dubhe Tower, hollowing out the load-bearing column and using some "black technology" to maintain its original strength was nothing more than a simple "experimental subject."
Even the technical difficulty was much less than the way of entering this room.
