The Cave Stream Scenic Reserve sits in Castle Hill basin - a low depression bounded by the Craigieburn and Torlesse Ranges. The name "Castle Hill" comes from the castle-like limestone outcrops which can be seen throughout the basin. The 594 metre cave within the reserve is one of the most outstanding natural features in the Canterbury region. From the car park, two tracks lead to the cave entrances. A short trail goes north to the upstream entrance, through a fascinating limestone landscape of solution holes, rillenkarren (water grooved rocks) and sculptured rock formations. The other track leads to the edge of a terrace overlooking the outflow entrance of the cave. It continues down the face of the terrace to the junction of Cave Stream and Broken River.The cave passage meanders and twists in total darkness between the two entrances. It takes approximately one hour to go through, but you need to be well equipped. Carry at least two reliable torches per person plus spare batteries and wear warm polypropylene or wool clothing and sturdy footwear. It's best to enter the cave at the outflow end and walk against the flow of the stream. There are several small waterfalls to climb. A rung ladder ascends the final waterfall, so that you can climb out of the cave.