Signed 25 years ago, the Valletta treaty places a strong emphasis on the protection of archaeological sites. Because of acute threats of archaeological site destruction by construction activities, a major result was a massive increase in rescue and preventative excavations on threatened sites. The Treaty also proposed that heritage assets should be preserved in situ, where feasible, and recommended member states share knowledge and training on this subject. Over the past 25 years a range of pilot projects and detailed one-off studies on specific sites have been conducted across Europe. In this session, we will discuss new insights we have gained into human and natural threats to archaeological sites, and practical ways to deal with them, including a) assessing and limiting the impact of construction on archaeological sites, e.g. the effects of piling and loading; b) determining the effects that agricultural practices, nature conservation projects and other rural land-use change have on archaeological sites and what mitigating measures are possible; c) developing and future-proofing protective measures and dynamic schemes for site protection; d) monitoring and assessment of the state of preservation of archaeological sites and materials, especially with regard balancing high-tech intense monitoring on few with low-tech extensive monitoring on larger numbers of sites; e) effects of climate change on the preservation of archaeological sites.@en