The coast south of Mahaiula. Basically, you go to Kekaha Kai State Park and take a left, through this gate:
The road is moderately difficult. Four wheel drive and a good clearance are necessary. From this angle, it's pretty obvious that Hualalai is a volcano:
Now and then, a roadway over the lava goes off to the right as you cruise south, toward the airport. There's a grey sand beach, plenty of cliffs, and a little storm beach with a grove of trees:
A little further south is my favorite site on this part of the coast:
A little more south and you can see the security fence around Kona Airport. A connecting road goes off mauka and connects to Queen Kaahumanu Highway about a mile north of the airport entrance.
This is all the Huehue lava flow came down in 1801 or so, from Puhia Pele, only at the 800 foot level or so:
Near the airport fence, there are several hornitos, little spatter cones. Click for a bigger picture (twice for an even bigger picture) of the detritus at the base of one: