Sima de San Pedro, Natural pit cave in Oliete, Spain.

Sima de San Pedro is a pit-shaped dolina in the municipal area of Oliete, south of the Sierra de Arcos on the northern flank of the Oliete syncline, near the old Monastery of San Pedro de los Griegos. Its funnel-shaped mouth measures about 65 by 90 m across and drops 120 m, with walls becoming nearly vertical and widening at the bottom around a lagoon 22 m deep.

The depression began as a karst complex of caves that water circulation and dissolution enlarged; when the cave roofs collapsed, the hollow left behind became this 120 m deep dolina en pozo. Loose detrital sediments on its outer rim, continuing toward the Martín riverbank, and its position in a ravine record that collapse. The lagoon at the bottom is fed by springs of the same ravine and by groundwater from the Martín, which near the sima runs 32 m above the floor.

The pit sits near the former Monastery of San Pedro de los Griegos and the Iberian settlement of Cabezo de San Pedro, both visible landmarks on the approach. Its name links it to Saint Peter, and the surrounding land is now open romeral scrub. The cave shelters red-billed choughs, alpine swifts, jackdaws, rock doves, starlings, house martins and rock sparrows, plus seven bat species.

The pit lies in the municipal area of Oliete, south of the Sierra de Arcos, near the old Monastery of San Pedro de los Griegos and the Iberian settlement of Cabezo de San Pedro. The rim is a funnel about 65 by 90 m wide, with walls that become almost vertical below and a lake 22 m deep at the bottom. The surrounding land is deforested and covered by mixed rosemary scrub.

The sinkhole shelters seven bat species and birds such as the red-billed chough, alpine swift and rock sparrow. On the access path near the Ermita de San Pedro grow some of the few Juniperus thurifera specimens in the Martín basin, linking the Iberian System and Monegros juniper stands.