4536: SubPhone entrance
Riaño 30T 451666 4800704 (Datum: ETRS89. Accuracy code: G) Altitude 171m
Length included in the Four Valleys System. (See Cueva Hoyuca) Depth 7m into Cueva-Cubío del Llanío, site 3234
Area position

Updated 19th February 2018; 12th May, 1st July 2018; 17th May, 19th September 2019; 19th September 2021

   Cueva-Cubío del Llanío was linked into the Four Valleys System on 31st July 2019. All caves which are part of the Four Valleys System are listed at the start of the Cueva Hoyuca description.

   After the discovery and survey of the Upper Mitre Passage in Cueva-Cubío del Llanío (site 3234) and exploring through Sandy Chamber and Side Road up to smaller passages with tree roots and some draught, it appeared that Llanío was heading for the surface. The survey indicated a densely vegetated area below a curve in the main road and the subsequent use of Ron Taylor's sub-phone equipment confirmed that station 3234-17-03.106 in Llanío was a very small number of metres below the surface. Hammering on the road was distinctly heard in Under Road Chamber and, again, the sub-phones were used to confirm that station 17-03.97 was under the tarmac. It would appear that the Llanío survey, carried out with a mixture of old and new technology, has been accurate to a couple of metres in all three dimensions.
    A second entrance was deemed necessary as the route to this area was tight and awkward in places. A new entrance here could cut 3 hours off a trip and allow fresher cavers to push at the end of Mulu Manners to a possible link with Cueva de Riaño (site 0105) - achieved in July 2019.
   The area was cleared of thick undergrowth and, after a false start, an area of rocks and clay investigated to a shallow limestone gulley sloping down on the same line as the passage below. By the end of the Easter "season", a 2m deep hole had been excavated mainly through clay with tree routes and the occasional lump of sandstone with an encouraging drill through the clay suggesting an open space about 60cm below. Although there was no guarantee that this excavation would provide a second entrance, the number of joints underground with roots and draught in places suggested that another route in would start in this area.
   See also Cueva Shelob, site 4173.
   Over the summer 2017, the dig progressed down to where a draughting hole was revealed and, eventually, a tight drop onto station 3234-17-03.106 in Llanío. In all, it took fifteen trips to complete the work: enlarging the entrance shaft to take a road drain lining and the bottom drop to accommodate larger cavers; concreting around the top and installing a lid. The photos and a video give a flavour of the efforts.
   When the entrance was used in January / February 2018, water from the road drainage system was entering the shaft, making for unpleasant muddy conditions at the base. Some surface diversions carried out allowed the draughting crawl at the base of the climb to dry out.
  A route to the cave through dense vegetation was cleared in July 2021 although no trips were carried out that summer.

References: anon., 2017b (Easter logbook); anon., 2017c (summer logbook); ; anon., 2019b (Easter logbook); anon., 2019d (summer logbook); anon., 2021c (summer logbook)
See also 3234
Entrance pictures : April 2017 : July/August 2017 : Infrared photos : Redder family trip Easter 2019 : summer 2019
Underground pictures :
Video : April 2017 work : Summer 2017 - From dig to entrance : Summer 2017 - explorations through SubPhone Entrance (YouTube) : aerial track over entrance, April 2018 (YouTube)
Cueva-Cuvío del Llanío linked to Cueva de Riaño, 30th July 2019 (YouTube)
Detailed survey : see Cueva-Cubío del Llanío survey
Line Survey :
On area survey :
Survex file :
Passage direction rose diagram: 1/7/2018