Hôtel-Dieu of Tonnerre, Medieval hospital building in Tonnerre, France.

The Hôtel-Dieu of Tonnerre is a medieval hospital with a vast stone hall featuring high Gothic vaults that extend over a considerable length. The space concludes with a polygonal apse where stained glass windows filter light throughout the interior.

Marguerite of Burgundy founded this medical institution in 1293 to serve the local community. Local quarries and forests provided the materials needed to complete the building in a relatively short period.

The name Fontenilles links the hospital to the springs that supplied it. Marguerite of Burgundy was buried in the choir of the Great Hall in 1308; her tomb was rebuilt there in 1826. The chapel holds a gilded Virgin about 2.10 m tall, carved around 1305, above a 16th-century altar.

The visit runs through the upper floor of the 1763–1767 extension, where the ticket desk and shop occupy the former cellar. The Grande Salle is 96 m long with the apse, 21.5 m wide and 20 m high, so allow time to walk its full length. The museum also shows fragments of medieval stained glass and a room set out as the ward looked in the 19th century. Exhibitions and concerts are held here from time to time.

A meridian line runs across the floor, installed in 1785 to function as a solar calendar tracking the sun's movement. This astronomical detail allowed people to follow the seasons and time of day based on how sunlight moved through the interior.