Trifter

A big hole. That’s the impression I had when I first looked to the abyss from the balcony on the edge of the huge sinkhole. San Pedro sinkhole is situated near the village of Oliete in Teruel province, in Spain. It is one of those hidden treasures not well known even among the people from the region. It is not so easy to reach and it is normally visited in a one-day excursion including Oliete and the nearby Cueva Foradada water reservoir. This is a desolated area, where the horizon is always far, poorly inhabited and where there is little tourist pressure. Villages are old, almost empty with hardly any job opportunities. In the surroundings there is a natural park along the river Martin canyons. In caves along the river there are some prehistoric paintings that attract some tourists and near Oliete there are also the ruins of an ancient Iberian fort about 2000 years old. Marine fossils are also quite frequent in the area around Cueva Foradada lake. I remember a slope totally covered by fossil oysters. They are so well preserved that separating the two shells it is possible to see the shape of the animal inside. In an area where human pressure is so low that animals have more space, and so once I saw a group of wild boars running and swimming across the lake.

San Pedro sinkhole is 108eep and a diameter of 95m on the top and 120m at the bottom. It was originated when the roof of an older cave was sunk, so, technically it is a doline. In the bottom there is a small lake of about 4000m2 and 20m deep. The first recorded descent took place by the beginning of the XIX century. The drop is quite a peculiar place in biological terms. It is the home of several species of birds and bats. Each of them nests at a certain depth inside the cave and enters and goes out of it always in a fixed order. First enter sparrows, barn and cliff swallows, starlings and pigeons. They are followed by red-billed choughs, jackdaws and finally alpine swifts. There are about six species of bats which wait for the last bird to get home before they go out. The process is repeated in reverse order at dawn when bats go back to the cave.

The lagoon is home to frogs, toads, little reptiles and snakes up to one and half metres long. Due to the many birds nesting in the walls of the cave, the water of the lake has a high content of organic matter. In the past the sediments laying at the bottom of the lake were extracted and used as fertilizer. Also In San Pedro sinkhole have been celebrated since 1988 international speleology competitions.

Photo: http://tracalet.iespana.es/actividades/simasanpedro.htm