Sima de San Pedro

Sima de San Pedro is one of Europe's most striking karst sinkholes, located in the municipality of Oliete, in the province of Teruel, Aragón, Spain. It sits between the villages of Oliete and Ariño, on the northern slope of the Oliete syncline, within the Sierra de Arcos mountain range.

What exactly is this site?

Sima de San Pedro is a collapse doline - a giant funnel-shaped opening formed when the roof of an underground cavern gave way. The mouth measures roughly 100 meters across (some sources cite closer to 65 by 90 meters), and the shaft plunges to a depth of over 100 meters, with figures ranging from 108 to 120 meters depending on the source. The walls, nearly vertical, widen toward the bottom, where a lake with a depth of 22 meters lies.

How did it form?

The sinkhole was carved by karst erosion driven by underground water connected to the Martín River. Researchers estimate the roof collapse that created the current shape happened somewhere between 750,000 and one million years ago. Because of its scale and geological rarity, Sima de San Pedro is regarded as a phenomenon without parallel in Europe, and it holds protected status as a Site of Geological Interest. The area falls within the Martín River Cultural Park and a Natura 2000 protected zone.

What will you see there?

From the viewpoint at the rim, visitors look straight down into the shaft - sheer rock walls dropping toward a blue lake far below. Nearby stand the remains of the old San Pedro de los Griegos monastery and the Iberian archaeological site of Cabezo de San Pedro, which gave the sinkhole its name. Descending into the cavity requires caving equipment and rope-handling experience; for most visitors, the appeal lies in the view from above and the surrounding Sierra de Arcos landscape.

What wildlife lives here?

The rock walls and crevices shelter more than 25 vertebrate species - amphibians, reptiles, birds, and mammals. Nine bird species nest in the cracks, including chough, swift, jackdaw, rock pigeon, starling, and swallow, while deeper inside the cave a bat colony of seven to eight species roosts, a population of real conservation value.

How do you get to Sima de San Pedro?

Access runs along the road connecting Oliete and Ariño. At a signposted turnoff, a side road covers about 2 kilometers to the parking area next to the sinkhole. The route is easy, though the final stretch runs on an unpaved track, so sturdy footwear helps.

When is the best time to visit?

Spring and autumn bring the mildest weather in this part of Aragón and the best daylight angle for viewing into the shaft. Summers in Teruel province can turn brutally hot around midday, so an early visit is worth planning during that season.

Frequently asked questions

Can you climb down to the bottom of Sima de San Pedro? Reaching the bottom requires specialized caving gear and rope-handling experience - this is a site for prepared groups, not casual visitors.

How far is the walk to the viewpoint? From the signposted turnoff on the Oliete-Ariño road, it's about 2 kilometers to the sinkhole, a stretch most visitors drive rather than walk.

Are there other sights nearby? Yes, the ruins of the San Pedro de los Griegos monastery and the Iberian archaeological site of Cabezo de San Pedro sit close by.

Is the sinkhole safe to visit? The rim viewpoint is set up for safe viewing from above, but given the vertical drop of over 100 meters, visitors should stay within marked areas and exercise caution.