The tombs are made of stonework and earthwork and some of them have large, detailed paintings inside them. Historians have found about 10,000 tombs from the Koguryo kingdom in China and Korea. Only about 100 of them have paintings on the inside. 80 of these painted tombs are in what we today call the Democratic People's Republic of Korea, or North Korea. 63 tombs are part of the World Heritage Site, and 16 of these tombs have paintings. They were chosen because their paintings are so detailed and show daily life, because the way they were built shows good engineering, because modern people can use the tombs to tell what the people of the Kingdom of Koguryo thought about burying people, and because the burials in the Kingdom of Koguryo affected many later countries, including the modern Koreas and Japan.