This group also includes the 120m Nakayama Otsuka tumulus (designated as a historical site by the prefecture), where broken pieces of a tokushu-kidai (ceremonial vessel stand) specific to the Kibi area were found in 1986, and based on the discovery, it was pointed out that the tumulus may have been constructed in the era when kofun tumuli started being constructed.
1986年に吉備的な特殊器台の破片の発見によって、古墳発生期まで遡る可能性の指摘された中山大塚古墳（120メートル、県史跡）がある。