Harry –
Where are these abandoned tunnels still with safe tracks leading into them, then?
(There were a few in Norway and one of the locomotives, German built, is now at Bressingham.)
Robert –
Falls, rotten timbers, structural collapse, anoxic or high CO2 conditions…. all very possible.
Mould spores, quite possible.
Breathing in asbestos fibres – only if something disturbs them enough to put them into the air. If the place is damp enough for mould then hazardous dust is not going to pose much risk.
Breathing in lead though? Hardly!
The ex-Norway, ex-Kreigslokomotiven locomotive at Bressingham Steam Museum. I photographed it last August when attending the miniature steam road-vehicle rally there. Apologies for the poor quality.