A vast expanse of territory in northern and eastern parts of occupied France comprising a total of six départements and parts of four others running from the mouth of the Somme to the Swiss frontier in the Jura. This area was separated from the rest of the Occupied Zone by a demarcation line and was effectively cut off from the rest of France. The terms zone réservée ("reserved zone") and zone interdite were often used interchangeably, but some sources distinguish a smaller forbidden zone, comprising parts of Somme, Aisne and Ardennes départements, from the larger reserved zone. This extra demarcation line never seems to have existed beyond theory.