Towards the end of May we were visiting Chateau Gaudrelle with clients and as usual it was one of the highlights of the day.
There are caves all through the Loire Valley which were originally limestone mines (read more here) and no matter the weather - from minus 20°C to 40°C - the temperature inside is between 12°C and 13°C with a humidity of between 85% and 90%. This is perfect for storing wine as the level temperature allows a steady ageing, and the high humidity ensures the corks don't dry out.
What I wasn't expecting to see was a proper mist inside the cave, I assume caused by how hot and humid it was outside. I am not quite sure what the science of it is, but it really was noticeable.
While I was there I also took a photo of some of the "Old Hoak Barrels" which are used to store the sweeter wines for two years.