We drive away from the mud pits and go up a small road. There is a big building along the road which is a large hydrothermal plant which is probably suppling must of the area with cheap energy based on the hot water in the ground just under the surface around here.
You can actually go inside the power plant and see a small exhibit about the production of power based on the hot underground water and watch a short video about the power plant.
From the power plant we continue a bit up the hill until we reach an old crater called Viti. You can do the short hike up the crater wall until you reach the rim of the crater. From here you can look down into the crater which has a lake with beautiful colours. There are a lot of people hiking around the crater – but nobody swimming in the lake – it might have something to do with the fact there is actually still patches of snow on the side of the crater so the lake is most likely very cold and not good for swimming.
If you are feeling very energetic you can hike around the crater – but there doesn’t seem to be much point in doing this since when you have reach a high point along the crater there doesn’t seem to be a much better view from the other side. Hence you might as well save your energy and time to explore other places in the area which will be more rewarding than walking around the caldera of Viti.