A few kilometres east of the lake, Kariandusi is one of the most important Stone Age sites in East Africa. Hand axes, cleavers, and other tools made of obsidian and lava lie scattered across the small excavation pits, much of it preserved roughly where it was found.
A small site museum displays a representative selection of finds and explains the geology of the diatomite-rich layers. The site sits on a hillside overlooking the lake — the views over the Rift are reason enough to climb up even if you are not a fan of stone tools. Entry is modest, and a local guide can usually walk you through the digs in half an hour.