From 1863, large-scale archaeological excavations took place at Izernore, in the Ain region, as some scholars believed it to be the location of ancient Alesia. At the request of Ain’s prefect, excavations began in July 1863, led by Étienne-Joseph Carrier and partly funded by the Commission de Topographie des Gaules. The excavations were completed in February 1864.

This plan was produced by Carrier in March 1864, after the excavations had been completed. We now know that Izernore is in fact ancient Isarnodurum, a secondary Roman settlement.