The paper is written by a geographer who is accustomed to exchange ideas with medieval historians concerning the topic of territory. Starting with an overview of the notion of "big territory", it questions why this term is so much used, nowadays, in the geographic and in the historical academic debate, and it gives a few arguments in order to strenghten the ties between both fields. Then, focussing on medieval mobilities and ways of life, the author underlines the skills (perception of space and ability to cross wide open spaces) used by men and societies, even in times of scarce information and resources. If the very local territory is well known and controlled through feodality, the big one (the kingdom or the Christiendom) can't be more than a mere ideologic or spiritual vision. Therefore, the paper shows the role of cities in the scaling of political power.