Awesome day exploring my new favourite orienteering area - a cave network in Fontainebleau. Just the most crazy place to spend 2 hours in. And the most amazing thing is they had an event there 5 years ago with 300 people running around the tunnels. So cool!
Link to map: http://omaps.worldofo.com/?id=72846
Would strongly recommend a look.
I also think there’s a YouTube video if you search ‘les mines du roi Salomon’....