Conservative issues on outdoor archaeological heritage: the Nymphaeum of the Tritons at Hyerapolis of Phrygia (Turkey) - from surveys to management system.

Intervention on archaeological heritage, especially in sites where surveys are still in progress, and where there are special issues with regard to environment and tourism, makes the development of a definitive project complex. In the present paper, these issues are examined through the experience obtained by the authors on the Nymphaeum of the Tritons, a monumental fountain located along the main plateia that crosses the roman-empire city of Hierapolis of Phrygia (Turkey). The Nymphaeum has been the subject of several archaeological digs during the last thirty years and is still being studied. It is configured as a complex system of layers, generated, for example, by the earthquakes of the third and 7seventh century AD, by subsequent settlement phases, but also by changes produced by archaeological investigations and measures implemented in recent years. The aim of the paper is to identify some invariants of the site, in order to direct the surveys carried out by the authors on the Nymphaeum toward a wider knowledge framework. In particular, the authors discuss some mutually related issues: the risks caused by economic and tourist valorisation and the risks incurred in the investigated area from an environmental point of view. This should allow the creation of a sub-management system, which, through a multi-scale, multi-criteria approach, defines shared strategic goals and identifies essential actions to pursue in the conservation and fruition of the monument.