On the Paris–Sens–Dijon TGV train route, Tonnere is a great base for exploring this corner of the region, and far cheaper than Chablis, just 18km away; the local golden, fruity Chardonnay is the newest appellation contrôllée in Burgundy, recognized in 2006. Although not as prosperous as its world-renowned neighbour, it is much prettier, since it was not bombed during the war – unlike Chablis – and it has several sights well worth a look.
Tonnerre is also an excellent starting point for cycling along the Canal de Bourgogne; from here to Dijon it’s four or five days of easy cycling through some superb countryside.
Tonnerre’s most unlikely attraction sits at the foot of the steep hill crowned by the church of St-Pierre. The Fosse Dionne is a fascinating blue-green “mystic” pool encircled by a wash house that dates from 1758. A number of legends are attached to the spring (the name derives from Divona, Celtic goddess of water), including suggestions that it was a gateway to hell or the lair of a ferocious basilisk slain by bishop St-Jean de Réôme. Divers have penetrated 360m along a narrow underwater passageway and 61m in depth with no end in sight, but further exploration was banned in 1996, after several explorers died in these attempts.