Caves, Springs, Groves and Mounds: Cult Places of the Ancient West

Start underground. The London Mithraeum was built around 250 CE beside the Walbrook in Roman Londinium, partly below ground in the cave-like form customary for Mithraic temples. It was found by chance in 1954 and drew crowds reported as high as 30,000 people a day.

The same cave form appears at the far end of the empire. Soldiers stationed at Dura-Europos on the Euphrates dedicated this mithraeum around 168 CE, and the embankment Roman defenders piled against the town wall during the Sasanian siege of 256 CE buried and preserved its paintings and dated inscriptions.

Here the sacred ground is a spring. Coventina's Well at Carrawburgh on Hadrian's Wall was a walled enclosure around the shrine of a Romano-British water goddess, and John Clayton's excavation of 1876 recovered thousands of votive coins, altars and carved water nymphs, one of the richest votive deposits in Roman Britain.

Lydney Park, built around 364 to 367 CE above the Severn estuary, shows what a pilgrimage sanctuary looked like. The temple of the god Nodens stood with a long dormitory where the sick slept hoping for a healing dream, a bathhouse and a guesthouse, and curse tablets found in the 1928 and 1929 excavations show how ordinary petitioners addressed him.

The path now moves to sacred trees. In the Genesis account Abraham received three visitors beneath the oaks of Mamre near Hebron. Herod the Great later enclosed the site with a massive stone wall, and Jews, Christians and Muslims have all venerated it, which makes it a useful comparison for the Germanic tree sites that follow.

A grove known from one text only. Tacitus, in Germania chapter 40, describes an island grove of the goddess Nerthus that only her priest could enter. He never names the island, and scholars have not agreed on which one he meant, so this site is a reminder of how much depends on a single classical witness.

A sacred oak near Geismar in Hesse, dedicated to Donar and revered by the Chatti. Its documented story rests on one event: in 723 CE the missionary Boniface felled it before a crowd to show that the god could not stop him, and he used the timber to build a chapel to Saint Peter on the spot.

The path ends in Denmark, where the change of religion is written in stone. At Jelling, King Gorm raised one runestone for his wife Thyra, and his son Harald raised the larger one with a depiction of Christ, recording that he had won Denmark and Norway and made the Danes Christian.