The Externsteine ([ˈɛkstɐnʃtaɪnə]) is a distinctive sandstone rock formation located in the Teutoburg Forest, near the town of Horn-Bad Meinberg in the Lippe district of the German state of North Rhine-Westphalia.

The formation is a tor consisting of several tall, narrow columns of rock which rise abruptly from the surrounding wooded hills.

In a popular tradition going back to an idea proposed to Hermann Hamelmann in 1564, the Externsteine are identified as a sacred site of the pagan Saxons, and the location of the Irminsul idol reportedly destroyed by Charlemagne; there is however no archaeological evidence that would confirm the site's use during the relevant period.

The etymology of the name Extern- is unclear, in older texts it is written as ”Estern” or Eastern (-steine meaning "stones" or "rocks").

Other scholars identify the association with magpies as folk etymology; Plassmann (1961) connects the name with a giant Ecke or Ekka of the Eckenlied, a medieval poem of the Theoderic cycle.

[4]: 1 The geological formation consists of a hard, erosion-resistant sandstone (so-called Osningsandstein), laid down during the early Cretaceous era about 100 million years ago, near the edge of a large shallow sea that covered large parts of Northern Europe at the time.

Above the entrance to the main chamber is a carving that unlike the others here is not a bas-relief, but simply a cut in the stone in the form of what appears to be a winged creature.

[4]: 13 The site is associated with archaeoastronomical speculation; a circular hole above the "altar stone" in the Höhenkammer has been identified in this context as facing in the direction of sunrise at the time of summer solstice.

[5] However, no archaeological evidence has been found that would substantiate use of the site between the end of the Upper Paleolithic and the Carolingian period (9th century).

Attribution of objects found was either to the Mesolithic Ahrensburg culture (see above) or to the medieval period, with evidence of occupation in the Bronze or Iron Age conspicuously absent: All the ceramic and metal items found were younger than the Carolingian period, some stone artefacts were attributed to the Ahrensburg culture.

In addition, a drystone wall east of rock II (not extant today) could be linked to buildings here mentioned in medieval documents.

Some additional records still exist today in photographs, but they can not be put into context due to the loss of written materials in World War II.

It records the purchase of a farm at Holzhausen including an Agisterstein by the abbot of the Abdinghofkloster [de] (abbey) at Paderborn from a female Saxon noble called Ida.

However, the inscription in the main chamber of the grotto mentions a consecration in 1115 by Henrico, which is deemed to be a reference to Heinrich II.

Historians have suggested, though, that this may be an indication that the abbey did not in fact claim the Externsteine for itself thus leaving them to fall into the bishop's purview.

[4]: 13–14 Some authors have argued that the ecclesial carvings and alterations to the stones may suggest use of the site as a Christian sanctuary from the early 9th century.

[4]: 13–14 [11] There remains a contradiction between the use of the Externsteine as a simple roadhouse for travellers and as an hermitage on the one hand and the presence of the monumental relief and the Arcosolium on the other.

The remains visible today indicate the possibility that the Externsteine were intended as a destination for pilgrims unable to travel to Jerusalem.

This was a fortress of two squat round towers flanking a central gatehouse, built against the eastern side of the Externsteine.

[4]: 18, 21 These improvements and better access via the road made the Externsteine an increasingly popular tourist destination, continuing a trend of the 18th century.

The period of Romantic nationalism of the 1860s to 1870s inspired a large number of publications speculating about the ancient history of the site.

Many of these were contributed by local amateur historians and published in the Zeitschrift für vaterländische Geschichte und Althertumskunde Westfalens.

[13] Local amateur historian Gotthilf August Benjamin Schierenberg (1808–1894) seems to have been the first to identify the "pagan idol" mentioned by Hamelmann with the Saxon Irminsul.

[4]: 23 From 1912 to 1953, a tramway ran along the Externsteine road, operated by Paderborner Elektrizitätswerke und Straßenbahn AG (PESAG).

[14] Today the preserve measures approximately 11 hectares (27 acres), and forms part of the ‘Teutoburg Forest’ nature reserve, Externsteine.

[16] Teudt could refer to a total number of more than 40 publications on the Externsteine, including eleven substantial monographs, most of which he considered outdated.

Interest in the location was furthered by the Ahnenerbe division within the SS, who studied the stones for their value to Germanic folklore and history.

[18] After the Nazis came to power, Teudt was put in charge of additional excavations at the site and appointed Julius Andree [de] to head the work done there by the Reichsarbeitsdienst in 1934/35.

He initiated the demolishing of tourist infrastructure (tramway, hotels) and the creation of a "sacred grove" or Heiligtum nearby.

[clarification needed] Because of its reputation as "pagan sacred site" in popular culture, there have often been private gatherings or celebrations on the day of summer solstice and Walpurgis Night.