Only remain the two walls South and West (24 m. high) of this square Gallo-Roman temple dedicated (wrongly) to god Janus: this was the cella, the closed part of a Roman temple. It dates back to the Ist century AC.
In the Middle Age, they called it tour de Genestoye, "tower of Genestoye", from the name of an old Roman district of Autun, located on the right bank of the river Arroux: Genestoye means a “place where brooms grow”... well, nothing to see with god Janus? Well, no! Progressively, the name Genestoye became Janus, we don't know why.
But do you know Janus? The famous two-faces god, one turns towards the past, the other one towards the future… Besides, we still don't know which god was worshipped here... but we still can see a niche, on one wall. Maybe a place where people put a statue of the divinity?
The famous French architect Viollet-le-Duc said that the temple was a simple gate which used to be part of the city rampart... but now we know that this temple was part of a huge complex of buildings: it was probably the place where the priests gathered, the famous cella.