period also refer to rites held by continental Germanic peoples in groves, including the sacrifices in forest clearings of survivors by the Cherusci after their victory at the Battle of the Teutoburg Forest, recounted by Tacitus in his Annals based on a report by Germanicus. Such groves were sometimes dedicated to a particular deity: in addition to the case of Nerthus, there was a silva Herculi sacra ('wood sacred to Hercules', an interpretatio romana) near the River Weser, and the Semnones reportedly held their rituals in honor of the regnator omnium deus ('god the ruler of all'). The scholar of Germanic religion Jan de Vries noted that placenames such as Frølund (Denmark), and Ullunda, Frösvi, and Mjärdevi (Sweden), in which the name of a deity is compounded with words meaning "grove" or "wood", suggest a continuation of the same practice, but are found almost exclusively in eastern Scandinavia; however, there is a Caill Tomair recorded near Dublin, an oak forest apparently sacred to Thor. Reverence for individual trees among the Germanic peoples is a common theme in medieval Christian denunciations of backsliding into paganism. In some cases, such as Donar's Oak (according to legend, felled by Christian missionary Saint Boniface), these were associated with particular gods, and the association of individual trees with saints can be seen as a continuation of the tradition into modern times. The Landnámabók, which describes the settlement of Iceland and dates from the 13th century, tells of a skáld by the name of Þórir snepill Ketilsson who, after his crew encountered and fended off raiding vikings, arrived in Iceland and founded a sacred grove there: ...Thorir took possession of all of the whole of Fnjoskadale, as far as Odeila. He made his home at Lund [Old Norse 'grove'], and held the grove sacred. Sacred trees and groves leave few archaeological traces, but two such sites may have been identified, both in Sweden. A mouldering birch stump surrounded by animal bones, especially from brown bear and pig, was discovered under the church on Frösön in Jämtland in 1984. The finds have been carbon dated to the late Viking Age. Possible burnt offerings have been found on a hill at Lunda near Strängnäs in Södermanland; the archeologist Gunnar Andersson has argued that the combination of the finds and the placename—which can mean "the grove"—point to this being the remnants of a sacrificial grove. Scholars have proposed that