Square Castan

Square Castan is an archaeological site in Besançon featuring eight Corinthian columns and ancient stone structures arranged within a garden setting. The site preserves remnants of water distribution basins that once connected to the aqueduct system supplying the Roman city of Vesontio.

The site displays remains of a large semicircular structure measuring about 54 meters across that once supported a colonnade in antiquity. This structure was long mistaken for a theater building before closer study revealed its actual purpose.

The square is named after archaeologist Auguste Castan, who led major excavations in 1870 and revealed important elements of Gallo-Roman architecture. Visitors today can see how his discoveries have shaped the way the site is presented and understood.

The site sits near the Black Gate monument and has interpretive panels explaining the findings on display. Access is straightforward, as the space is openly arranged and serves as a public garden that visitors can walk through freely.

The structure was originally a water supply facility rather than a theater, as was mistakenly believed for many years. This confusion reveals how challenging it can be to interpret ancient structures without careful examination.