The 2446 stone steps to the top of Haguro-san (419m) have been worn down and smoothed by centuries of pilgrims. The mountain's easy access makes it the most popular of the three peaks, particularly with day trippers.
At the base of the mountain in Haguro village, the Ideha Bunka Kinenkan has exhibits covering the history of the mountain and yamabushi (mountain priest) culture, though there is little in English.
The climb, which begins by passing through the torii (shrine) gate and over the bridge, takes a leisurely hour. En route you'll pass Gojū-no-tō (五重塔), a weather-beaten, five-storey pagoda dating from the 14th century.
An ancient teahouse known as Ni-no-saka-chaya marks the halfway point. Stop in for sets of filling mochi (pounded rice cakes) and revitalising bowls of matcha (powdered green tea). If you detour to the right, you'll come upon the temple ruins of Betsu-in (別院), visited by Matsuo Bashō during his pilgrimage here.
Dewa Sanzan-jinja sprawls over the summit of Haguro-san, intermingling with the cedars. At its heart is the San-shin Gōsaiden (三神合祭殿), a vivid red hall that enshrines the deities of all three mountains.
If you're completing the circuit, your only option from here is the bus – most of the old 20km pilgrim trail along the ridgeline to Gas-san became overgrown after a road was built in the 1960s. Catch a bus from the parking lot beyond the shrine bound for Hachigōme (八合目; eighth station), where the trail to the top of Gas-san picks up again. Note that the last bus leaves just after 2pm. Alternatively, you can stay the night at the atmospheric Saikan.