Ogof Draenen* (Hawthorn Cave) is by far the biggest cave in the Pwll Du area. It is the most extensive cave in Wales and is a globally-significant system. At the time of writing it is 37th longest in the world, and still has huge potential for exploration.
The cave was first entered in October 1994 by members of Morgannwg Caving Club after almost four years of digging. It quickly became clear that a very significant discovery had been made. In only two months, 20km of passage had been explored and exploration was continuing.
The official length of the cave cannot be determined until the Grade 5 Survey is complete, but is understood to be well over 70km. This makes it the second longest in Britain.
Draenen has resisted significant extension in recent years, but digging and exploration is ongoing. There is potential for extension in the rarely-visited north end of the system, and to the east is situated The Blorenge. This is a mountain full of limestone that appears to drain into Draenen but has very little associated cave.
However, the main focus of exploration is to the south. It is known that several major streamways in the cave resurge at Pontnewynedd and Snatchwood Risings, several kilometres distant from the end of the current known ends of the cave; many kilometres of cave clearly still await discovery. The quest for the Mystery Streamway continues.
See Access for details of how to get a trip into Draenen.
* Can be pronounced as either oh-gohv DRY-nun or DRAY-nun, depending on whether you’re feeling South Walian or North Walian respectively.