During the Roman period it developed into a powerful military fortress, and then into a municipium and religious center, during the time of Emperor Marcus Aurelius. During the reign of Emperor Justinian the fortress was rebuilt.
Troesmis lost its urban function in the first half of the 7th century and regained it in the 10 - 11th centuries. Archaeological research started in 1860 when Emperor Napoleon III sent an archaeological mission on site, led by Gustave Boissiere, by Ambroise Baudry and by Ernest Desjardin. The group carried out a number of small-scale research campaigns between 1865 and 1868.
The Google map can be found here and some picture from Wikipedia Commons follow: