This is Hawaii's largest, ancient place of worship that is still intact. The heiau was constructed completely out of lava rock in the 14th century during the reign of the Pi'ilani Dynasty.
The stone platform is the size of two football fields. The area was overgrown until the 1970's which kept the site a secret and therefore in excellent condition.
Take Highway 360 (Hana Highway) east toward Hana. 'Ula'ino Road is off the left near Mile Marker #31. Just after a mile down the road it gives way to broken pavement and the first stream ford. Beyond the ford, to the right, you'll find the entrance to Kahanu Gardens, an extension of the National Tropical Botanical Garden. If the ford has water flowing through it above the pole-markers, turn around and do not try and cross the stream.
The 122-acre garden is home to a variety of rare native Hawaiian plants and several trees introduced by the Polynesians. The garden also has one of the largest known collections of breadfruit trees. A mile long trail meanders through the garden, allowing visitors to be their own tour guide. Beyond the forest edge you'll find the impressive and colossal Pi'ilanihale Heiau. Visitors are not allowed on the heiau, so you'll have to view it from afar. The coastal views here are beautiful.
The last time we checked, the garden was open Monday - Friday, 10 a.m. - 2 p.m. Admission is $10 for adults and free for children. It closes without notice, so don't be surprised if you find Closed signs.