Start behind Hilo Hawaiian Hotel (4:03am), Follow Bayfront, Turn up Kaumana (follow until merge with saddle road), Continue up saddle road until turn right on Mauna Kea Access road. Follow access road up to visitors center (public fountain to refill water here) then continue on to summit, Finish up and around the little summit trail to the top of the caldera! 44.36mi
As you will see in my GPS data, had a few massive cramping sessions after the access road turn. Just went out to hard down low and not recovered well from my marathon 2 weeks ago... This could easily go 2-3 hrs faster.