Were they filled in after the war or just abandoned? There were so many of them it must have been a massive clean-up job, or take up too much space to just abandon.
Most of it has been ploughed or built over but some still exist where the land has been preserved and left untouched.
Examples include:
Vimy Ridge where the Canadian Memorial is sited. There are sections of trench that have been preserved with concrete 'sandbags' as well as sections of tunnels and mines that were dug.
Here is a photo I took at Vimy
Also, Delville Wood where the South African memorial is sited.
At Vimy, you are prohibited from walking off the beaten track due to the quantity of unexploded ordinance, but you can go 'off piste' at Delville Wood and marvel at the higgeldy-piggeldy ground.
Sections of Verdun are also preserved as well as Sanctuary Wood near Ypres.
The Zone Rouge (Red Zone) refers to areas where human activity was prohibited due to the danger of unexploded ordinance. Although the zone is shrinking, farmers still dig up old shells (the Iron Harvest) with their ploughs and tractors and specialist team hunt the stuff. They tend to recover around 900 tons of unexploded ordinance a year.
I have seen these old corroded shells stacked by the roadside awaiting disposal. They could be anything from shrapnel or high explosive to mustard gas. Strictly not for touching!
