The Touraine is riddled with underground passages and quarries. Even the shortest drive will take you past at least one, with its entrance temptingly open to the road. Many of them are seemingly empty and some of them are complex systems of interlinking chambers and passageways going deep into hillsides and cliffs.
the Château de la Celle-Guenand
I was interested to note that there are no signs (eg guano) of bats roosting in the caves at the château. At this time of year, many bats switch from their summer roosts in trees and buildings and move in to a cave for the winter.
Rhinolphus ferrum-equinum Grand Rhinolphe fer à cheval
The troglodyte complex at Gatineau below. Vienne Nature has posted a warning about disturbing bats here. I assume there are Greater Horseshoe Bats in residence, as I found one dead on the roadside 10 days ago.
In the neighbouring départements of Vienne (86) and Indre (36) you will often come across notices at cave entrances, reminding you that bats are protected. This is an indication that the site is a known bat roost, and you should not enter. Our département, Indre et Loire (37), is much less likely to post warning notices, and I know of one cave, very easy to access, which has at least four species of bats currently hibernating in it. Fortunately, there is no evidence that they are in danger of deliberate disturbance.