The point of conserving and restoring monuments is to preserve them as works of art and as historical testimonies. There are various ways of slowing down the deterioration of ruins, which have usually suffered considerable weathering through long exposure to the elements. Restoration is a highly specialised process which is absolutely vital to the preservation of the monuments, even though it reduces their authenticity. Because of this, the ruins have to be documented and studied in great detail both before and during restoration, so that the intervention will be effective and respect both their historical and their aesthetic value. Documentation based on a historical investigation is the first stage of the project, its purpose being to make a detailed survey and plan of the monuments, record their historical phases, building techniques, and condition before restoration, and diagnose the problems. The latter step leads directly on to the second stage of the project, which involves proposals for dealing with the causes of deterioration. The principles that are followed (discreet, visible interventions, reversible solutions, use of traditional materials) are internationally accepted and conform with the international charters for restoration.