Le Yaudet is a promontory of granite commanding the estuary of the river Leguer down-river from the modern town of Lannion (Cotes d'Armor). It has long been known as the 'Old Town' (Civitas vetus in Latin documents and Coz Yaudet in Breton) and Iron Age, Roman and medieval finds have been made from time to time over the last two centuries. A programme of research excavations began in 1991 and continued annually until 2002. The results of the work show the site to have been in use almost continuously from the early prehistoric period. This publication is the first of four volumes documenting the fascinating discoveries made at this important site. Written entirely in French, it provides an overview of the site, giving insight into the physical geography, the town's history prior to excavation, and the archaeological research programme. It is lavishly illustrated with many photographs and line drawings.