Some of the mausoleums were left in ruins as the imperial family declined in power during the medieval period, while others, like the tumulus which is believed to the tomb of Emperor Ankan, were converted into castles of Sengoku daimyo (territorial lords in the Sengoku period).
中世になり天皇家の力が衰えると荒れ放題となる陵墓もあり、中には伝安閑陵古墳のように戦国大名の城として改造されたものまであった。