[en] The CRN Trisaia, located in Basilicata in Southern Italy, is the reference site for CNEN's research and development programme on disposal of long-lived radioactive wastes in clay formations. The Trisaia Centre is in an area characterized by relative tectonic stability, despite its proximity to the Apennine orogen. The site is located a few kilometres from the Ionian Sea on a Quaternary terrace, a few metres above the elevation of the coastal plain. The terrace materials, which are mainly sand, gravel and conglomerate, are underlain by 800 to 1000m of marly clays. Some sand lenses are contained in the clay formation nearby the site, particularly between 350 and 500m in depth; however, thick sections of homogeneous clays have been crossed by all exploratory bore-holes drilled in the area. The marly clays are Plio-Pleistocene and contain about 70% clay minerals and about 20% calcium carbonate. Their colour is blue-gray at depth, while at the surface they are yellow as a result of weathering. The permeability is of the order of 10^-8cm/s. A heating experiment was performed with an electrical heater placed at a depth of 8m. However, the results are somewhat questionable due to the defective plugging of the holes where the heater and the thermocouples were positioned. A second heating experiment is now planned; it should employ three heaters at a somewhat greater depth; both pressures and temperatures will be measured. Many additional geological, engineering and safety studies are planned on the Trisaia clay formation. (author)