Tom Scott has a great video[0] about the Onkalo spent nuclear fuel repository in Finland[1], in which he talks about one of the reasons that they decided on the particular area - why would anyone dig there? Skip to 4:29 in the video for the relevant info.

[0]: https://youtu.be/aoy_WJ3mE50

[1]: https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo...