I was walking on the bridge part, straight down to the famous shouting statue. I noticed the middle of the road is made up of a lot of rocks, and to the left is a great view of the volcano. I noticed a sign saying Hikinohiragawa (引ノ平川), there’s no river but a lot of ashy grey rocks. I did do some research and there a special Lava Trekking Path Program you can take for 2 hours for a fee, might have more info at the tourist centre but I didn’t know about it until much later. If I ever revisit Sakurajima, I’d love take up this opportunity.