A very long tunnels under the sea from Scotland to Turkey? It's just hard to see how they built it. Without a mechanical ventilation system, the low points of the tunnel will be filled with CO2 and other non-respirable pollutants, condensation, and other problems. No lasers, so how can they keep the tunnel running across the large distance while digging?
source: https://alien-star.org/ancient/12000-year-old-ancient-underground-tunnels-discovered-connecting-scotland-with-turkey/
