The numbers tell the structural story. The north tumulus is a two-tiered construction with a diameter of 38.6 meters and a height of 6.8 meters. The south tumulus is larger and more elaborate -- a three-tiered mound 55.4 meters across and 9.4 meters tall. Together, they stretch 85.8 meters in total length. A double-circular moat with an average depth of 1.4 meters surrounds both, giving the entire complex a footprint of 104 meters including the water. Fukiishi -- cobblestones arranged on the surface as a decorative and structural element -- have been found on both tumuli, though only on the west side of the narrow constriction where they join. No haniwa, the distinctive clay figures that typically adorn kofun exteriors, have been recovered. Stone rows line the third tier of the southern mound. The construction style dates the complex to the latter half of the 6th century, the twilight of the Kofun period.

The north tumulus holds the more fully explored burial chamber -- a large stone room stretching 10.6 meters in total length. Inside, excavators found two house-shaped sarcophagi carved from tuff, one placed in the main chamber and a second in the entrance vestibule. The stone coffins mimicked the ridged rooflines of actual buildings, a funerary tradition reserved for individuals of considerable status. Grave robbers reached the chamber first -- likely in the early 7th century, barely a generation after the burial -- but they left traces behind. Archaeologists recovered glass balls, silver rings, horse harnesses, iron swords, and earthenware scattered among the disturbed remains. The southern tumulus also appears to contain a horizontal stone chamber, but it has never been fully excavated, preserving whatever secrets it holds for future generations.

Local legend assigns one of the two tumuli to Prince Saegusa, said to be a son of Prince Shotoku, the near-mythical regent who championed Buddhism and centralized governance in 7th-century Japan. The archaeological timeline makes the connection strained -- the mound likely predates Prince Shotoku's lifetime by at least a few decades -- but the persistence of the legend suggests that whoever lay in these house-shaped coffins was remembered long enough for their identity to become entangled with the most famous prince in Japanese history. The dumbbell shape itself invites speculation: were these two individuals buried simultaneously as part of a shared ruling arrangement, or was the second mound added later to honor a successor? The sealed southern chamber keeps its counsel.

Archaeological excavations in 1946 provided the first systematic look at the site, followed by more thorough campaigns in 1993 and 1994. Since 1995, the Kanayama Kofun has been maintained as a public park in the town of Kanan, on the Kanan Plateau at the western foot of Mount Katsuragi. The surrounding paddy fields, sitting lower than the ancient moat perimeter, frame the twin mounds in a patchwork of green and brown that shifts with the seasons. Designated a National Historic Site of Japan in 1991, the kofun is accessible via a three-minute walk from the Seryutani bus stop on the Kongo Bus line from Tondabayashi Station. Standing on the park grounds, with the forested slopes of Katsuragi rising to the east and the Osaka plain stretching westward, the dual mounds feel less like an archaeological curiosity and more like a deliberate statement -- two circles fused together, holding their dead close across fourteen centuries.