Unfortunately, landmines are a small part of a large problem: unexploded munitions last centuries. Artillery, rockets, grenades, mines, explosives, even large ammo dumps can stick around and explode decades later.

Here’s an active one from WW1 that is still uninhabitable because of the danger:

https://education.nationalgeographic.org/resource/red-zone/

The intense fighting and shelling near the tiny town of Verdun has permanently altered the region surrounding the Meuse River in northeastern France. The environmental destruction left by the battle led to the creation of the Zone Rouge—the Red Zone. The Zone Rouge is a 42,000-acre territory that, nearly a century after the conflict, has no human residents and only allows limited access.