Just after the 6-mile marker en route to Mauna Kea's summit area from MKVIS, pull into a paved parking area. Below is the trailhead to Lake Waiʻau, the third-highest lake in the USA, and Keanakakoʻi, a protected ancient Hawaiian adze quarry. It'll take an hour or so to hike to both the lake and the quarry, depending on your level of fitness and acclimatization. To say there is a palpable sense of the sacred here would be an understatement.
Entering the quarry is discouraged, because it's a fragile archaeological site of importance to Hawaiians, but the views from the trail are still worth seeing.
