A very complex cave system. Most entrances require the negotiation of pitches, with some routes very tight. Rivers run in the lowest levels creating sporting streamways and flooded sections while upper levels contain large decorated passageways. The RRCPC site has a description (in sections).
The cave is divided into several major sections, with potential in several places to connect with other nearby caves:
- The first is Easegill Caverns, which consists of multiple small tributary passages creating a maze-like structure, draining the nearby Easegill stream into Lancaster Hole's streamway. Lancaster Hole then forms the backbone of the section, with large passageways. It is joined by other tributaries from the other side of the backbone. The entire system is often referred to as Easegill, after this section.
- The second major section is Pippikin Pot, which consists of a tight pothole into a mature cave network, draining the far side of Easegill. This is then connected through Link Pot to the first major section.
- The third major section is a network of flooded passages starting at Pippikin Pot, draining to the resurgence caves at Witches Cave and Leck Beck Head. The flooded network also connects the fourth major section.
- The fourth major section consists of the caves of Gavel Pot and Lost John's Cave. Both of these are potholes, with Lost John's being a very extensive vertical network. Long Drop, Death's Head Hole and Big Meanie, once their own conjoined cave, also form part of this section.
- The fifth major section consists of the caves of Notts Pot and Ireby Fell Cavern. The Ireby Fell entrance enters a series of pitches leading to a semicircular shaped main stream passage. Two sumps must be passed (the first can be pumped or bypassed, but the second is divers only, sorry) to enter Notts Pot. Notts Pot has entrances leading to what must be the most complex vertical maze in Britain with several choices of routes. Most routes eventually reach the sump which leads into the well decorated Notts 2 with its terminal sump, and alternative dry entrances.
- The sixth and currently final section consists of the caves of Large Pot and Rift Pot, reasonably large passages connected to Ireby Fell Cavern through tighter passages. Importantly, these drain in the opposite direction to the main flow, into the currently unconnected Kingsdale Master Cave, showing that future connections could provide a very extensive cave system of around 114 km.
The cave holds several records, though it is worth noting that for nearly 15 years, it lost its status as the longest connected cave to Ogof Draenen, a status that it regained in November 2011. It is currently the longest cave in the British Isles, and has the potential to become much longer by being connected to other caves. It has the longest overland length of any cave in the British Isles at about 6.18 km. It has the longest overland distance between entrances, at 4.89 km between Bull Pot of the Witches and Large Pot. It has more entrances than any other cave system in the British Isles (45 I think, but there may be more). It also holds the dubious honour of having had more deaths than any other cave in UK or Ireland in modern caving, with a total of 17. This is due, in part, to the fact that there is so much passage length in the system, and that the cave is split into several smaller caves and potholes. If historical deaths are also counted, then the Three Counties System holds second place, after Dunmore Cave.
This system has a history of greatly exaggerated length estimates. When Ogof Draenen started to pose a threat to the title of Longest Cave, the Easegill surveyors estimated 100 km of length. This was later revised to 75 km. However, in August 2010, Descent issue 215 revealed that a more accurate estimate for the length of the then-connected cave was around 60 km, and since about 1996-1997, Ogof Draenen had in fact been the longest cave in the UK. It was given only a year to enjoy its rightful status, as on the 6th of November 2011, Notts Pot was connected to Lost John's Cave, bringing the total to an estimated 86 km. Subsequent connections and explorations increased the length to its current amount. A very carefully prepared estimate in the February 2012 issue of Descent 224 gave the revised length of 86.922 km. Subsequent connections and extensions brought the estimated total to just under 89 km. Subsequent corrections and removal of duplicated passage lengths reduced this to 86.619 km in the October 2014 issue of Descent 240, in spite of the recent additions. This is still an estimate - the true length may be a little higher or lower, and will continue to increase as discoveries are made.
The total depth of the system is gained between the Large Pot entrance and the 64 metre deep upstream sump in Gavel Pot, giving equal first place for depth-below-an-entrance, shared with Ogof Ffynnon Ddu. The deepest through trip in the system is 189 metres, between Large Pot and Leck Beck Head, though much of that route lies underwater.