T145 Pozo Del Castillo

Includes: T304 Clockwork - T145 Pozo Castillo - Pozo Natacha - Segura I (Castillo V) - Segura II (Castillo IV) - FT16 (Castillo III) - FT17 (Castillo II)


CO-ORDINATES: 30T X:360600 Y:4785570
LENGTH: 1985m
DEPTH: -293m (-309m to bottom of Pozo Natacha)


Alternate Names





Pozo del Castillo






Castillo 2






Castillo 3






Castillo 4

Segura 2





Castillo 5

Segura 1





Pozo Natacha[1]






Torca del Reloj

T304 - Clockwork Pot












From Caseton de Andara, follow the markings for the Lake Depression (Pozo de Andara). At the obvious junction (before reaching the lake area) take the left hand path that zig zags up the side of the mountain, until the obvious mine area is reached. The entrance is the highest (T145), it is very easily located by its large dimensions (8m by 15m).

The opening is at 1840m altitude at the left of the path. (see sketch of the zone).


Large 13m entrance pitch. (8m x15m diameter).  Segura 2 entrance is easiest and safest way in (albeit wet)

Picture: Entrance


Note: Sistema Castillo is the Spanish name given to a collection of caves that link together underneath the Minas de Mazarrassa area of Andara, including Pozo del Castillo, Pozo Natacha, Segura 2 and Torca la Reloj (Clockwork Pot).  Historically, these caves have been documented as distinct caves, as and when they were discovered, and have inconsistently been described in relation to the overall system.   

The large (8m x 15m) open entrance is 13m deep to a floor of boulders and a snow plug in the middle.  An obvious opening on the southern wall drops down to the second pitch of 15m with more modest dimensions.  Over the top of the second pitch are numerous mine workings that require re-exploration and surveying.

Flooded Mine Adit

At the bottom of the 2nd pitch into Pozo Castillo, straight ahead leads up a short climb to two small pools of water.  An obvious passage on the right is flooded, with mine debris under the water, the passage bends at around 10m and appears to continue.  

Castillo Upper Series

At the bottom of the 2nd pitch into Pozo Castillo, turn right down a mine passage, with wooden steps, for 20m to a junction.  

The routes straight on and up extends for 30m over a lot of spoil material to an obvious boulder collapse.  There is no obvious route through the boulders.  The original 80’s description referred to almost 1km of unsurveyed passage in the area but this appears unlikely as there is only one mined passage.  The passage is heading steeply up and back towards the area seen over the top of the 1st pitch in Castillo.  Exploring over the top of the pitch may find this missing passage.

Just before the passage starts to ascend there is a minor junction, with a hole in the floor and a passage on the right.  The hole leads to a tiny chamber with a small animal skeleton before connecting back up with the right-hand passage. 

The right-hand passage leads to a number of interconnecting chambers with stacked deads, running parallel to the main route, connecting at various places.  There are no other obvious leads in this area. 

Main Junction

Back at the junction after the 2nd pitch turn right and follow the main passage for another 30m to the main Pozo del Castillo junction.  Straight on leads to the Segura 2 entrance and right leads to Pozo Natacha. 

Left at the junction is the main way into Pozo del Castillo, the mine passage descends downwards past stacked deads and contains a strong draught.  The first passage on the left, after 10m, connects back to the Upper Series.  The second passage on the left, after 40m, is the Upper Crawl.   

Upper Crawl

The passage begins on the left-hand side, where the main route enters a chamber with stacked deads on both sides creating an obvious passage down. 

Climbing up on the left-hand side, and over a narrow bridge above the stacked deads leads to a steeply ascending passage with some tricky stemple climbs to negotiate, the biggest being 2m high.  At the top of the climbs the passage bends right and takes on a more natural cave appearance, with mud and rocks evident.  Following a sharp left bend, a noticeably draft is detected emitting from a tight rift.  The rift can be pushed to a 4m climb into a boulder choke.  The way on has not been pushed but this route is most definitely heading back to the surface

Back in the main Castillo passage the route trends north for 25m before turning left.  A 3m climb on the right leads to a small chamber with a deep pool.  On the far side of the pool the in mine passage continues, half flooded, this has not been pushed to a conclusion. 

The main Castillo passage continues and passes a small crawl on the right, this leads to a descending tight boulder filled passage for 5m to a sharp left turn.  The passage then goes up via some small climbs in mine workings.  Not explored. 

Stemple Way

Just before the main passage descends steeply a route on the left leads to Stemple Way.  The passage ascends via a spoil heap to a 12m pitch up, that would require aid climbing.  A passage on the right just before the pitch, passes over a number of old stemples to an obvious pitch head.  The pitch is 10m back down to the main Castillo route.  There is a possible lead 2m higher, above the pitch head. 

The main passage continues and passes a small crawl on the right, this leads to a descending tight boulder filled passage for 5m to a sharp right turn.  The passage then goes up via some small climbs in mine workings.  The route here connects back up with the Castillo passage close to the start of Stemple Way. 

Routes to FT16/FT17

After another 20m, in the main passage, another small crawl on the right is the main way on into the Pozo del Castillo 1983 series.   

Before entering the crawl the main passage continues up into further minor workings and an obvious climb down under the mine workings leads to a sharp right angle bend into a small chamber.  Just beyond the chamber is the main FT16 entrance chamber, with the passage entering 20m below the entrance pitch head.  The Segura 1 entrance adit is 10m above this point (where an obvious winch platform can be seen), however, it is not easily accessible from this point. 

The crawl is flat out for 10m and leads to a small chamber, straight up and to the left, daylight can be seen, this is the top of the FT16 entrance pitch.  To the right is a pitch up to daylight, and this is assumed to be FT17. 

Another small crawl forward leads to another small chamber with a snow plug and large propped boulders above.  Beyond the snow blockage is the way on the Pozo del Castillo 1983 series.   

Pozo del Castillo 1983 series. 

A small squeeze on the right of the snow plug leads further into the chamber, but since the early 1980’s no one has passed this point, as it is believed to have collapsed considerably since the initial exploration.  This collapsed area is presumed to connect to Castillo III (FT16) and Castillo II (FT17) but is unconfirmed and not surveyed.  Revisiting these other entrances would be worthwhile, in case they provide an easier way past the blockage. 

The floor of the chamber can be reached by sliding under the snow plug for about 10m, then a new drop reaches a rift, 2m wide by 3m high, The Walk of the Metamorphosis. This leads to a pitch of 6m where the draught is very strong.  The bottom of the pitch quickly leads to another 12m pitch, with snow on one side, to another pitch of 30m in an elongated shaft of 10m x 20m.  There is possible continuation over the top of the 30m pitch. 

At the bottom there is another snow patch leading steeply down to two successive pitches of 7m and 12m into a circular chamber of 15m diameter.  

The cave then takes a sharp 90-degree bend continuing along a lightly decorated rift before enlarging at the top of a 40m pitch.  There a series of parallel pitches over the top of the 40m pitch that connect back at the base.   

At the bottom of the 40m pitch is a 3m climb, followed by two superb cylindrical pitches of 7m and 10m.   The cave drops another several metres before continuing in a large passage, The Whistling Meander, 2m wide by 5m high for 100m.  The cave then starts to narrow to a small trickle of water coming in from an impenetrable inlet and downstream leads to a final rift, Thatcher’s Squeeze at -293m. 

There is a loud sound of water from beyond the final rift and a very strong draught throughout this section.