Accessed via a 1.4km path from the Narusawa Ice Cave, Fugaku was also formed by prehistoric lava flows from Mt Fuji, you'll need to crawl through some tight ice-walled spaces here to see what was once used as cold storage.
Fuji-Yoshida's oshi-no-ie (pilgrims' inns) have served visitors to the mountain since the days when climbing Mt Fuji was a pilgrimage rather than a tourist event. Very few still function as inns but Togawa-ke Oshi-no-ie offers some insight into the fascinating Edo-era practice of Mt Fuji worship.
Get up to speed on Mt Fuji at this well-presented visitor centre. An English video (12 minutes) with blockbuster movie soundtrack is a little cheesy but gives a good summary of the mountain and its geological history. There's also an observation deck and restaurant.