This is one of our favourite caves in Thailand. Five hundred and ninety two steep steps and a tight squeeze take you into a stadium-sized chamber full of shimmering limestone formations, amazing both in shape and colour. It's 12km northwest of the main entrance of Erawan National Park and park entry fees apply: flash the same entrance ticket if you've just visited Erawan Falls.
Rangers wait at the cave mouth to lead people on a raised track and tell you (if you understand Thai) about the geology and biology of the cave. They have lights, but bring your own if you can.
Note that you need to be at the cave mouth by 4pm, and the climb can take up to half an hour.