From Surabaya will takes you 8 hours to Banyuwangi, a district on the most east of the Java. Banyuwangi and Bali is being separated by a narrow straits as you may see through the coastal road. From Banyuwangi, it is about 2 hours more to get to the foot of the mountain, then hike for a few more hours to the peak to see the turqoise coloured acid crater lake.
On your way hiking up, you will pass people carrying yellow coloured chunks. Actually, the crater lake is the site for sulphur mining operation. Those people are carrying that minerals by using baskets manually by hanging it on their shoulder, walking up for a few kilometres from the crater floor to the cliff crater, then walking down through the path of the mountain slopes to get paid. On the halfway, the labours will stop at a station to weight their loads then again to finish the journey at Pultuding Valley to redeem the wage. Do some kind efforts which is highly appreciated, bring some food and offer them, some of them are very old, hungry and skinny.
The yellow coloured chunks are actually the sulphur, mineral that being produced by the reactions in volcano activity. Sulphur is widely used in cosmetic industry, especially for skin beauty.