These are pictures of the Halemaumau crater at Kilauea. They're taken at several spots along the trail from the Volcano House hotel to the Jaggar overlook.
The trail is a nice walk. It's about 2.5 miles, one way over mostly flat ground. Starting at the Volcano House, you meander through a wet forest. As you get further away, the landscape changes from a forest to a desert. Instead of lush green trees, you're walking through barren cinder from the volcano. It's an interesting transition on such a short walk. At several points along the trail, the Halemaumau crater comes into view. These are the pictures below.
I've heard people say that they've visited the park and were underwhelmed. While I didn't have this reaction, it's easy to understand. You're basically looking at a steaming hole in the ground. It's a very large hole, filled with molten rock, but still just a hole. So if you're not into nature or geology, you should be prepared. It's definitely not for everyone, but for those that are interested, it's pretty amazing.