The necessity of managing world heritage cultural sites for their sustainable development: the case of the Delos archaeological siteMost of the monuments included in the list of World Heritage Cultural Sites simultaneously constitute magnets for international tourism whilst at the same time being global treasures that require special conservation, in order that they may be preserved for future generations (i.e. made sustainable) and maintain their educational and social role through time. The first step in the necessary conservation of World Heritage Sites is the development and implementation of a management philosophy. The attempt to formulate the management principles of a particular site constitutes the foundation for all subsequent initiatives. In this respect, the planning process consists of three steps: 1) making an inventory of the existing resources, 2) categorising and evaluating those resources, and 3) determining the necessary properties for legislation, financing, human resources, infrastructure, conservation interpretation, and marketing (all of which are based on the evaluated inventory). A crucial step in the management procedure is the creation of a structure concerning staffing and budgeting, policies on visitor-related income, image and marketing, recording and analysing visitor as well as local population data. The case study of the Delos archaeological site is being presented in order to demonstrate the strengths and weaknesses of, and the opportunities and threats surrounding, one of the World Heritage Sites of greatest significance in Greece. Delos, being in the centre of the Aegean Sea, constitutes a major tourist attraction from which Greece can obtain important socio-economic benefits, which can simultaneously, with appropriate management, be accompanied by sustainable development.