Pu'u o Mahuka is the largest heiau (traditional Hawaiian temple) on Oahu, covering about two acres on a hilltop above Waimea Bay with sweeping views of the North Shore coast. The heiau consists of large stone enclosures built from the volcanic rock that covers the hillside — the walls are intact to several feet in height in places, and the scale of the construction, achieved without metal tools or wheeled vehicles, is impressive.
Access is via a short drive up a steep road from Pupukea Road, followed by a brief walk to the site. The views from the heiau are among the best on the North Shore: the bay below, the coastline curving toward Haleiwa and toward Sunset Point, and in winter the white water of large swells visible in both directions. The site is a State Historic Monument, and the heiau is still considered sacred by many Hawaiians — offering bundles of ti leaves are often visible at the walls. Treat the site with the same respect you would give a functioning religious place.