Description of the caves
Now let’s go through the descriptions of the Caves of Oliero, one by one. The Covol dei Siori description is divided into three sections: the tourist section, the diving section and the upper branches, a logic that does not apply to descriptions of other chambers. The descriptions of the underwater sections are based on reports and findings of divers who have visited the deepest areas. Please note that underwater exploration conditions are critical and therefore cave descriptions provided by divers are sometimes inaccurate.
Tourist section
The rectangular entrance is about 3 metres high and 12 metres wide. The Oliero river flows fast along the cave bottom. Walking upriver for 20 metres, you come across a lake with a depth of 13 metres. This lake is fed by the sump below and water emerges to form the Oliero river, along with the spring in Covol dei Veci. Taking the boat across the lake, whose waters reflect the stalactites and concretions hanging from numerous niches and chimneys on the cave roof, you alight on the internal landing stage and find yourself facing a huge rift (Crepo dee Soree) where the Oliero river once sprang forth. You continue onwards into the Sala della Colata (Chamber of Flows) where an enormous calcareous flowstone covers a wall of the chamber.
The upper branches
The Rami Alti, or upper branches, open out in the upper section of the Sala della Colata, 20 metres off the ground. These branches can be explored to a distance of 150 metres and are divided into two: Ramo Fossile (the fossil branch) and Ramo dei Pantani (the mud branch). After walking 20 metres down a funnel 3 metres wide and 0.8 metres high, you reach the Sala delle Candele (Chamber of Candles). A myriad of stalactites hang from the roof and the same number of stalagmites rise up from the cave bottom. Their unusual shapes inspired Giovanni Abrami to give that section of the cave its name. On the left, going down Ramo Fossile, you reach the Saletta Amadio chamber, named in honour of the sadly deceased Amadio Negrello, the first president of the Gruppo Grotte Giara Modon. Here also you can admire an incredible variety of calcareous concretions and deposits in the form of stalactites, stalagmites, eccentric concretions, straws, pools and festoons. The end part closes with a section 1 metre wide and 3 metres high. The bottom is sandy and muddy.
The right branch, Ramo dei Pantani, takes its name from its muddy bottom. The branch is reached through a passage artificially carved in the mud. Once you are through this passage, you intercept the Ramo dei Pantani branch. Crawling on hands and knees for about 20 metres, you enter a chamber 2 metres high, 10 metres wide and 10 metres deep. There are also plenty of stalactites and stalagmites here that are often joined up to form columns. This is where the section of the cave accessible on foot ends, although numerous small passages lead off from here.
The Covol dei Veci cave
The cave opens at the base of a vertical rock wall about sixty metres high. It starts with a large chamber with an imposing rock face about 20 metres high. The cave roof has blind chimneys that climb up a few metres. The roof is decorated with ivy trailing right down to the surface of the water. On the right, walking very carefully along a narrow ledge, you can venture into the cave for several metres without getting wet and view the interior, although it is much easier and safer to stay on the left of the cave, after crossing the Oliero river on the little dam bridge and walking through a section of the park.
The bottom of this huge majestic cavern is filled with water that creates a stunning covered lake. The water may be still in dry periods, or seething with stones that shoot into the lake when the cave is active. The lake bottom is initially about 3 metres deep and completely covered with large pieces of rubble, from a huge landslide that came down from Valleranetta in 1936 and invaded both the Oliero river basin and Covol dei Veci, modifying the aspect of both. Diving down you proceed along the first funnel of mixed gravel and finer sand that easily muddies the water in the passage. At -9m the scarce natural light that filters weakly from the first part of the lake, disappears and the cave plunges into total darkness ahead. You proceed down a vertical passage marked on both right and left sides by live rock.
You can observe strange markings formed by chemical erosion that look like tiny pinpricks. This passage is the narrowest point in the cave, even though it is about 3 metres wide. Once you have gone down this passage, at -32 m down, the passage opens out to about 20 metres wide and 12 metres high. The first thing you notice is a huge mass of shale, from the external landslide. This is the area where you are most likely to spot Proteus. Several fortunate dive groups have seen three specimens at a time. The large gravel funnel begins at this point too. It is almost all fine gravel, about 1-2 centimetres in diameter. On the right of the funnel the gravel is quite well-washed, although flippers will easily fan up suspensions. On the left instead, where the current is noticeably not as strong, there are muddy patches and numerous, and also bulky plant remains that were dragged into the chamber by the landslide of 1936. Going further down, still in the gravel funnel , you get down to -40 m, where there is a U-shaped piece of iron embedded in the gravel, known as the “grapnel”. Again, this is material brought down by the landslide.
The grapnel is a set reference point for divers and a check point for equipment and the dive, as well as a handy anchor point for lanyards. The gravel funnel continues down to -50 m, and where the gravel ends, enormous round boulders appear, that form the bottom of the passage down to -55 m deep, the deepest point in the first part of the chamber which usually marks the limit of recreational dives. Here too, with a little luck, you may see Proteus or another unusual visitor to these zones, the mudskipper, brave enough to dive so far deep down and so far in. It is not unusual to even find a few trout and for a while people worried that the trout might present a risk for the survival of Proteus. Subsequent sightings proved there was nothing to worry about. The gallery continues, with colossal dimensions towards the belly of the mountain winding this way and that, heading more or less south-westwards. Its deepest point is about 600 metres from the cave entrance where it drops to about a limit of -59-60 metres, then continues to ascend gradually to finally re-emerge after 2,400 metres. According to descriptions by Olivier Isler, the cave continues dry along a round conduit.