The Roman Empire, Middle Ages, Renaissance and the following centuries of the history of Italy have left many cultural artefacts that attract tourists. In general, the Italian cultural heritage is the largest in the world since it consists of 60 to 75 percent of all the artistic assets that exist on each continent, with over 4,000 museums, 6,000 archaeological sites, 85,000 historic churches and 40,000 historic palaces, all subject to protection by the Italian Ministry of Culture. As of 2018, the Italian places of culture (which include museums, attractions, parks, archives and libraries) amounted to 6,610. Italy is the leading cruise tourism destination in the Mediterranean Sea.