Yayoi period is Tatetsuki Mound Tomb in Kurashiki, Okayama. The mound is about 45 metres wide and 5 metres high and has a shaft chamber. Broken pieces of Tokushu-kidai, cylindrical earthenware, were excavated around the mound. Another prevalent type of Yayoi period tomb is the Yosumi tosshutsugata funkyūbo, a square mound with protruding corners. These tombs were built in the San'in region, a coastal area off the Sea of Japan. Unearthed articles indicate the existence of alliances between native tribes in the region. Early Kofun period One of the first keyhole-shaped kofun was built in the area, the southeastern part of the Nara Basin. Hashihaka Kofun, which was built in the middle of the 3rd century AD, is 280 metres long and 30 metres high. Its scale is obviously different from previous Yayoi tombs. During the next three decades, about 10 kofun were built in the area, which are now called as the Makimuku Kofun Group. A wooden coffin was placed on the bottom of a shaft, and the surrounding walls were built up by flat stones. Finally, megalithic stones formed the roof. Bronze mirrors, iron swords, magatama, clay vessels and other artifacts were found in good condition in undisturbed tombs. Some scholars assume the buried person of Hashihaka kofun was the shadowy ancient Queen Himiko of Yamataikoku, mentioned in the Chinese historical texts. According to the books, Japan was called Wa, which was the confederation of numerous small tribes or countries. The construction of gigantic kofun is the result of the relatively centralized governmental structure in the Nara Basin, possibly the origin of the Yamato polity and the Imperial lineage of Japan. Mid-Kofun period During the 5th century AD, the construction of keyhole kofun began in Yamato Province; continued in Kawachi, where gigantic kofun, such as Daisen Kofun of the Emperor Nintoku, were built; and then throughout the country. The proliferation of keyhole kofun is generally assumed to be evidence of the Yamato court's expansion in this age. However, some argue that it simply shows the spread of culture based on progress in distribution, and has little to do with a political breakthrough. A few tombs from the mid-Baekje era were excavated around the Yeongsan River basin in South Korea. The design of these tombs are notably different. The tombs that were discovered on the Korean peninsula were built between the 5th and 6th centuries CE. There remain questions