Corfe Castle has a particularly commanding position, on top of a small but steep-sided mound, part of the great chalk ridge of Purbeck Hill, which stretches 15 miles across south Dorset and forms a natural barrier between the main part of the county to the north and the undulating land of the Isle of Purbeck to the south. The castle hill is separated from the main ridge by two narrow valleys at either side, both eroded by little rivers, which provide natural routes through the main hills, and hence this has long been recognised as an important location to defend, amongst other reasons to counter the possibility of invaders moving north from the nearby coastline.
The castle was one of the first to be built by the Normans, starting around 1080, and its importance is evident since right from the start the fortification was constructed in stone, in contrast to the more usual motte and bailey design, which featured wooden buildings enclosed by an earthen embankment. The castle was extended in two main phases, early and late in the 12th century, and remained in royal ownership until 1572, when it was sold. It was later involved in the Civil War, after which, in common with many other English castles, the structure was deliberately damaged (slighted), in order to prevent any future military use. Here, this action resulted in parts of the castle, although still standing, being left in sections, at odd angles, and this is one of the main attractions of the castle, together with its lofty position that affords grand views in all directions, its relatively large size, and the variety of architectural features. Because of these factors, and the general photogenicity of the ruins, the castle is a very popular place; it is managed by the National Trust, and typically ranks amongst their ten most visited places.
The castle lies along the A351 about half way (5 miles) between Swanage and Wareham; like the Swanage Railway - now a heritage line travelled by steam trains - the road runs through the narrow valley just east of the fort. The southeast side of the hill is the least steep, and here the outermost walls of the castle border a quaint village, also named Corfe Castle, which has some limited parking places, but in general visitors to the castle have to leave vehicles further away. One place is along the main road past the hill, by the junction with a lesser road through the western valley, while just opposite, on the north side of the A351, is the main National Trust parking area, plus a small visitor centre. However both these are often full at popular times in which case the next closest is a park-and-ride facility at Norden, half a mile away. The rides are not always an operation, however, so then people need to walk an extra quarter of a mile, on a path. Whichever parking is used, the final approach to the castle is the same; along a path beside the Corfe River on the west side of the hill, and then another path to the south, still following the river, rising gradually towards the village and ending beside a road at the castle entrance. In recent years the steep, grassy slopes below the castle have been home to a flock of soay sheep, an unusual, hardy but somewhat endangered breed, originating from the St Kilda islands off the north coast of Scotland.
Corfe Castle contains three main enclosed areas (baileys, or wards), each surrounded by walls, at successively higher levels of the hill, culminating in the great keep at the summit, at the centre of the inner ward. The largest section is the outer bailey to the south, comprising about two thirds of the total area; this is surrounded by an outer wall with the gatehouse at the south, flanked by two towers, and other towers at intervals along the sides, in varying states of preservation. The far edge is delineated by a ditch and a steep slope to one side and a shorter wall at the other, containing a second gatehouse which gives access to the west bailey, surrounded by higher surviving walls and three more towers; from here another slope rises further to the inner ward, right at the top of the hill, location of the main buildings - the keep, gloriette (residential building), hall, chapel and various lesser rooms. Like most houses in the village, the castle is constructed from the local Purbeck limestone, pale grey in colour.
Tickets for the castle are purchased from a National Trust office in a building just outside the entrance; visitors proceed across a wooden bridge over a ditch then through the outer gatehouse, contained between two stout round towers. Two more towers define the southern corners of the enclosure; that to the west (the first tower) is slumped at about a 30 degree angle away from the vertical, while that on the opposite side (the horseshoe tower) is properly upright, though missing all of its interior wall. This tower is used to display historical exhibits. The path from the gatehouse crosses the wide grassy lawn of the outer bailey, past the second, third and fourth towers on the west side and the plukenet tower (named after Alan de Plukenet, constable) to the east, then continues over another bridge above a ditch, and through the southwest gatehouse, also known as St Edward the Martyr's gatehouse. This is still relatively tall, but completely split into two sections, one also slightly off-vertical. Ahead is the west bailey, which contains the foundations of the original (late 11th century) hall, and is protected by three more towers, named south, north and butavant, or dungeon. A final short climb reaches the top of the hill, which is dominated by the jagged walls of the keep, some of which are over 50 feet tall. On the north side of the keep are a number of huge pieces of fallen masonry, also positioned at varying angles, while to the northeast are the photogenic remains of the gloriette, dating from the 13th century. The keep contains several intact rooms at ground level, and a central passageway which leads to a fine viewpoint on an open platform, originally the bastion.
As expected for such a prominent location, the hill at Corfe Castle has long been used for defensive purposes, at least since Saxon times, though the later fortification has covered nearly all traces of the original structures. The old English king Edward is believed to have been murdered at the Saxon castle in 978. The Normans began construction a few years after the conquest, and stone components from this stage included the wall of the inner ward and part of the hall below; the outer fortifications would at this stage still have been made of timber. The next major addition was the keep, completed by Henry I at the start of the 12th century, closely followed by walls and towers of the west bailey, and then the gloriette at start of the next century, plus the curtain walls of the outer bailey, together with all their supporting towers and the gatehouse. Not so much changed over the next 300 years, for most of which time the castle was one of the five designated royal palaces in the country, until declining military needs led to its sale by Elizabeth I, to Sir Christopher Hatton, Lord Chancellor. Ownership passed to Sir John Bankes (Attorney General) in 1635, and after seeing action during the Civil War, the then derelict castle was abandoned, though it remained with the Bankes family until 1980, when the ruins were donated to the National Trust, together with most of the adjacent village. Many of the buildings in the village use stones salvaged from the castle ruins.