If it was logistically easy to sink air shafts, it would have been done a long time ago, just to vent hot air, long before also using that heat was an idea. It

If it was logistically easy to sink air shafts, it would have been done a long time ago, just to vent hot air, long before also using that heat was an idea. It's a densely built up area. Space above and below ground is hard to find.