Kinkeisan, the Golden Chicken Mountain, is not much of a mountain, just a wooded hill rising at the edge of Hiraizumi, but it was important enough to the Northern Fujiwara that they buried a sutra on its summit. In 1124 or thereabouts, according to tradition, a sacred text was placed in a bronze cylinder and buried here, with a golden figure of a chicken said to guard it, and that gave the hill its name. A small shrine marks the top, among tall cedars.
From the summit, on a clear day, you look over the paddies of the Kitakami valley and across to Chuson-ji's ridge and the rest of the old capital's scattered remains. The hill sits in the line of the old city, with the original axis of Hiraizumi pointing toward it, so the Fujiwara seem to have designed their paradise around it. Ancient hiking paths wind up through the forest, steeper than you expect, with stone steps worn by pilgrims. Moss and ferns cover the rocks.
The Fujiwara story is why this matters. Their wealth came from gold in the northern mountains and from trade in horses and furs, and their rulers, Kiyohira, Motohira and Hidehira, built a city of temples, pagodas and gardens that rivalled the capital. The family sheltered the famous young warrior Minamoto no Yoshitsune, and when his brother Yoritomo, the shogun, demanded him, the Fujiwara hesitated and then fell. The relics of the city that remain, the golden hall and gardens, are the survivors of that fall.
Ichinoseki is the nearest town of size, about nine kilometres off, and has fuel, restaurants and hotels. There is little at the foot of the hill itself, so expect quiet. Visit early in the morning when birdsong fills the woods. Autumn colours light up the slope, and in winter snow covers the paths, making steps slippery. Wear shoes you can walk in, and leave helmets locked to the bike.