The Nag’s Head is a distinctive granite rock formation on St Agnes in the Isles of Scilly. The island is known for its unusual weathered rocks, but this outcrop is especially noticeable because its upper section resembles the head of a horse. Standing around 15 feet, or 4.5 metres, high, it is one of the better-known natural features on the island. The formation is most likely the result of long-term natural weathering and erosion. Wind, rain, salt, and temperature changes have shaped the granite over thousands of years, creating the appearance that gives the rock its name. Similar forms can be seen across the Isles of Scilly and West Cornwall, where granite outcrops often take on shapes that resemble animals, faces, or human figures. The Nag’s Head has also attracted antiquarian interest. William Borlase, the Cornish antiquarian, suggested that places like this may have been used by Druids for ritual activity. There is no firm evidence to prove this, but his interpretation reflects the way earlier writers often connected striking natural features with ancient religion and sacred landscapes. Even without proven ritual use, the rock’s appearance and position would have made it a memorable landmark. In prehistoric and historic landscapes, distinctive stones and outcrops often became reference points for movement, storytelling, and local identity. The Nag’s Head fits into this wider pattern of natural formations becoming culturally meaningful through name, tradition, and repeated attention. Geologically, the Nag’s Head is part of the granite that underlies St Agnes, the Isles of Scilly, and much of Cornwall. This granite belongs to the Cornubian batholith, formed around 290 million years ago. Over time, erosion exposed and shaped the rock into the forms seen today. The Nag’s Head is therefore both a geological feature and a named landmark within the wider historic landscape of St Agnes.