I knew nothing about this incredibly special place when I visited, and I wish I had. So, for you, future visitor who might also be a bit dorky for history/fun facts, some information from Visit-Dorset.com: Durdle Door is a "... part of the Jurassic Coast. The coastline is of such international geological importance that it was designated England's first natural World Heritage Site by UNESCO in 2001 and is now part of a family of natural wonders including America's Grand Canyon and Australia's Great Barrier Reef. The magnificent natural limestone arch was formed when the power of the waves eroded the rock and forged a hole through the middle. The name Durdle is derived from an old English word 'thirl', which means to pierce, bore or drill."
I visited via the car park (which has toilets) located on the cliff top. The walk downhill to the viewpoint is quite steep and pebbly, and can be slippery when it's raining, so wear good shoes! It's about a ten or fifteen minute walk depending on the weather, your physical ability, and popular times of day/year. On a sunny day especially, the view of Durdle Door is incredible from here (as are the famous white cliffs); the water looks almost Mediterranean! If you're from the US: carry in, carry out when visiting. If you're from the UK: respect, protect, collect when visiting.
SIDE NOTE: if you're going to Lulworth Cove, there are boats (Jurassic Rib Rides, I think?) that will actually bring you up close and personal with the Durdle Door archway if you'd like a more intimate experience/different perspective! read more