ABSTRACT: Increase in urbanization development represents nowadays a trend which is common to many European mountain regions. New residential areas are in most of the cases related to winter tourism attraction and specifically to ski resort locations. Likewise, the existence of nature protection areas is able to influence urban space demand in their surroundings and even to lead to what is known as naturbanization. Together with the intense use of land for urbanization, land abandonment characterizes mountain landscape. As a matter of fact, urban development exerts a great pressure on agrarian activities, which run the risk of becoming marginal or even disappearing. In this paper the case of the Pyrenean valley known as Vall Fosca is addressed. It is used as an example of current dynamics in Pyrenean landscapes: ongoing land abandonment and the implementation of an economic model based largely on tourism, thus bringing about an intensive urbanization process.