The limestone arch standing at Durdle Door was carved by wave action over 10,000 years, its Portland stone folded into a perfect curve during the Alpine orogeny 30 million years earlier. The formation sits within the 95-mile Jurassic Coast, England's only natural World Heritage Site, where 185 million years of geological history lie exposed in the cliff faces between Exmouth and Studland Bay. The name derives from the Old English 'thirl', meaning bore or drill, a reference to the circular perforation the sea punched through the headland. Durdle Door tours from Bournemouth traverse 18 miles of coastline, passing through West Lulworth village before descending the clifftop trail. The site became accessible to the public in 1970 when the Weld Estate, which has owned the land since 1641, opened footpaths across its holdings. The beach below the arch remained relatively unknown until the 1980s, when improved car parking and coastal path signage brought increasing visitor numbers. By 2010, the location had appeared in dozens of films and television productions, cementing its status as Dorset's most photographed natural landmark. The geological drama extends beyond the arch itself. Man O'War Beach lies immediately east, sheltered by chalk stacks that mirror the erosion patterns at Old Harry Rocks eight miles north. To the west, Scratchy Bottom valley leads toward Swyre Head, the highest point on the South West Coast Path in Dorset at 208 meters. The cliffs here expose the Purbeck and Portland limestone beds that define the entire coastal stretch, their horizontal stratification contrasting with the vertical chalk bands further east. Marine biologists note that the waters surrounding the arch support populations of spider crabs, cuttlefish, and occasionally bottlenose dolphins migrating through Weymouth Bay. Jurassic Coast excursions from Bournemouth typically include both Durdle Door and Lulworth Cove, where a horseshoe-shaped bay demonstrates differential erosion at work. The combination allows visitors to witness two distinct geological processes within a single morning. Kayaking adventures to Old Harry Rocks extend the coastal narrative northward, tracing the chalk ridge that once connected Dorset to the Isle of Wight before post-glacial sea-level rise flooded the intervening lowlands 8,000 years ago.