0458: Hidden Hole
S Vega 30T 450784 4795116 (Datum: ETRS89. Accuracy code: G) Altitude 340m
Length 2211m Depth 130m
Area position

Updated 30th August 1998; 19th February 1999; 2nd May 1999; 14th May 2000; 10th June, 28th September, 8th October 2001; 6th May, 26th October 2002; 25th May, 17th October 2003; 1st February 2006; 1st July, 28th October, 5th November 2009; 6th January 2011; 22nd April 2013; 27th September 2015; 30th June 2018

The entrance, with a fluctuating draught, lies in the shakehole behind the scar that holds Hammered Hole (457). The grid reference noted from Google Earth could be 30T 0450778 4795109 but this has yet to be checked on the ground.

A small rift leads to a tight vertical drop into a larger rift passage. At a chock-stone a 10m pitch drops into 5m of rift passage to a tight pitch head. Gloom Pitch (57m) is rigged from a Y-hang and a short deviation; a second deviation 9m down gives a 31m hang to a 3rd deviation (in situ) from a ledge on the far side of the shaft. The 2009 survey revealed a window leading into a chamber about 15m -20m down with further prospects. This was checked out at Easter 2013 and 0.4 x 0.4 window entered to a 4m diameter chamber with a flat floor. The continuation is in a rift to a p5 that appears blind.
At the foot of the pitch a ramp slopes up to a choke passing below two high avens. Down slope, a low arch leads to a short section of walking passage and a sharp right turn enters a large, well decorated passage. At Easter 2013, "from top of boulder slope at bottom of Gloom Pitch, a climb may lead into a tube in the roof (may require 2 bolts for progress and protection."
Following the left hand wall passes a scramble down to an undescended pitch (20m+?) a walk through Column and Stal Grotto then a short traverse brings you to the head of a rift, at least explored in an Easter 2003 visit when 10m pitch was bottomed and the northern side appears to continue with loose rock. Following the right hand wall, climbs up reach the foot of the ramp, oxbows which are yet to be pushed are seen, then various ways on lead to the head of the rift mentioned above.
A pitch down into the rift is rigged via a small passage that leads to a section of decorated passage and pot (undescended) and a window on the left looks down into the rift. At the foot of the pitch a passage to the NW leads to a dig in sand and gypsum; to the SE a climb up reaches a pitch and section of passage that appears to be below the large, decorated passage first entered.
At the foot of Gloom Pitch, SE across the ramp, a short traverse passes the head of a pitch that ends in boulders and a bedding enters a short section of passage with a slope to a short climb down and a further sandy slope that leads to a large, sloping passage.
Straight ahead leads to Sherwood Forest - a complex of narrow, sharp, inter-connected rifts leading to a sloping blind pitch and a pitch of 32m. This drops to a cross passage that extends 20m SW-NE each side of the pitch. The SW passage has formations ends in soft mud walls which may dig. Another drop of 8m reaches an altitude of 215m. Sherwood Forest was searched for continuations at Easter 2013 but no extensions were found.
Left up the slope leads into a large area of  boulder choke with many sections of solid passage, rifts and climbs which don't appear to go anywhere except back towards the p32.
Downslope leads via short climbs or pitches to an unexplored rift below Robin Head Traverse. Robin Head Traverse starts part way down the slope and leads to a section of passage sloping down to the rift. At the end of the traverse, a tight narrow rift leads to an aven with a way on at the bottom which passes back along a narrow rift, but is not fully explored.
A 20m pitch near the start of Robin Head Traverse also needs descending.
The Good Friday the 13th Extensions in Juan Lombrero that end at a 5cm high bedding appear to come very close to Hidden Hole and Hammered Hole.
The draughting dig beyond a 10m pitch to the west of the cave was hammered out at Easter 2013 and pushed for about 6m until a 20cm hole was met - with uncertain potential.

Easter 2002 Extension - Slip Sliding Away
(The description above may need changing)
An easy climb up at the base of the ramp leads to the start of a section of well decorated passage with short traverses and false floors.
A small decorated passage on the left connects to a rift (visual only); second left leads via a sandy crawl to the head of the rift (above) and pitch down (base previously seen).
The next passage (first right) Daggers Crawl leads back to the ramp in known cave and further small passages which appear to connect back to known cave (oxbows shown?)
The main passage leads to an unexplored pit and climb up to a smaller decorated passage. This opens up on the right, dropping to an undescended pitch. Left continues large past an unexplored pit to a traverse over a false floor where a 20m rope is required.
The main passage continues large over mud slopes, with possible ways on the left to mud slopes up to a junction. Left goes to a climb and tubes not explored; right, a climb down leads to a chamber with a rift in the floor. Tubes lead off at floor level and a hole can be seen above.
This point is close to Cueva Cefrales (site 42).

2009 Extensions through Squeezing Column Passage
Following the western passage from the bottom of Gloom Pitch, where it enters the grotto and turns right, there is a passage to the left, just 2 meters past the dripping water inlet (climb 1 meter up). It is worth noting that Jonas Binladen and Torben Redder on one of the last trips many years ago had a really good look around the inlet, but missed Squeezing Column Passage. Squeeze past the 3m x 0,2m column into a walking size passage with a few squeezes. The passage ends in a unpassably tight place, that was located from the other side, about 5 meters away, from another place in the cave. Half way along the walking size passage, there is a p15 (2 spits required). This drippy pitch leads to a muddy slope down and a steep phreatic tube sloping up (use about 20 m of rope for belay up the tube) leading to Dining Chamber through a hammered hole. From Dining Chamber, Precarious Tube leads to the bottom of the muddy slope at the end of the p15. There are a lot of avens in the new area. A place that needs a second look is the chamber west of Dining Chamber, as this was surveyed at the end of the final 18 hour trip.
At Easter 2013, the pitch near the start of Squeezing Column Passage was dropped. This is a 16m drop to a blind pit. About 3m off the floor towards the north there is a) a ramp of boulders, going about 8m up with no way on and b) 3m towards the east into a wet aven, about 6m high. Footprints and a sling from unknown exploration was found, but no way on.

August 8th Extensions (2009)
In the northern end, the c6 climb starts off the eastern side of the wall. The entrance window is well decorated with stals (roof and floor). The main passage is walking size, mostly with a flat floor. At the southern end the passage ends in an opening of about 2x2 m with a p16. Thi pit has not been descended, but connects into known passage. In the middle of the main passage there are small passages (complex tubes) but there seems not to be a way on.

An overnight trip at Easter 2013 had the misfortune to drop a tackle sack containing milk, water and a DistoX down Gloom Pitch. This destroyed the liquid containers and appeared to break the DistoX. The team camped and slept on a flat mud floor 50m WNW of the main pitch, found plenty of drinking water, but were unable to survey the (small) extensions made.

A hydrology diagram for the South Vega System can be seen here.

Radon measurement over 24 hours (31st March - 1st April 2013) gave a reading of 1400 Bq/m3

References: anon., 1983a (Easter logbook); anon., 1983b (logbook); anon., 1998d (logbook); anon., 2000b (Easter logbook); anon., 2001b (Whit logbook); anon., 2001c (summer logbook); anon., 2002a (Easter logbook); anon., 2002b (summer logbook); Corrin Juan, 2003a (photo); anon., 2003b (Easter logbook); Corrin Juan, 2003b; Corrin Juan, 2005; Corrin Juan, 2009; anon., 2009b (Whit logbook); anon., 2009c (summer logbook); Corrin Juan, 2010; León García José, 2010 (Volume 1 and Volume 2) (photo); anon., 2013b (Easter logbook); Papard Philip, Corrin Juan and Smith Peter, 2014; anon., 2015c (summer logbook)
Entrance picture : yes
Underground picture(s): entrance passage : summer 2001 : Easter 2003 : 2009 explorations : Easter 2013 bivi

Video: Easter 2013 - exploration and bivouac (YouTube)
Detailed Survey : Before the 2001 extensions, showing proximity to Hammered Hole 1:500
2001 survey (1:1000) with projected elevation2002 Easter survey (1:1000)
end 2002 planend 2002 projected sectionEaster 2003 plan (pdf version) (some alterations from end 2002 plan)
2009 survey : Easter 2013 text additions
Line Survey :
On area survey :
Survex file : yes (2009) (Amended magnetic declination December 2013 to align with Eur79 grid and coordinates altered to fit ETRS89 datum, April 2014.)
Passage direction rose diagram: 30/6/2018