Dathan C.
Yelp
The Pu'u U'alaka'a State Park consists of three public parts, a short hike, a picnic area, and the lookout that views southern Oahu, stretching from Kahala to the Wai'anae mountain range and mount Ka'ala, the tallest mountain on Oahu.
The short hike starts nearly right after the entrance to the park after the gates and is a very short, less than a half a mile (I think) that is super kid friendly. The large grassy picnic area is next to the also large parking lot. Due to the altitude and relative shade, it's fairly cool. There are some benches and a public bathroom.
But seriously, no one comes for those two amenities. It's all about the view. To get to the lookout, take the left fork at the first parking area and drive to the end. There are only about 10 stalls, often take up by tourists flocking in for the panoramic view. If you can't get parking here, drive back to the first lot and walk the short distance back to the lookout. The parking lot itself has a gorgeous view of Manoa valley, and if you're lucky, you can see a rainbow, or even double rainbows.
The lookout itself is a concrete, railed square, connected to a covered pavilion with placards giving history about Oahu. There's also a large, sloping grassy field in front of the concrete lookout. It can be exceedingly crowded with huge numbers of people taking pictures and enjoying the view. The grassy field is enclosed by heavy vegetation and kids will often run around. It's one of the nicer places to have a sunset picnic dinner. It can be extremely sunny and hot during the afternoon here as there's almost no shade outside of the pavilion, so wear sunscreen.
Do not leave ANYTHING valuable or suggestive of valuables in sight in your car. Cars have been broken into many times here, even in broad daylight, so take everything valuable or put in your trunk before you get there. Hours vary for the seasons, with the parking closing between 5:45 pm and 7:45 pm and the park rangers WILL throw you out at closing (ahem, speaking from personal experience). Hours are changed based on sunset times as the state does not want to have to deal with people at the park at night. This is also an amazing location for photographing a rising super moon.