So the south-west bank of the Severn estuary and west of the oolite hills. It is a very varied stretch of undulating country, cut into two by the line of the Mendip Hills. This district exhibits a greater diversity of scenic feature and building materials than is to be found in any corresponding area in England. This is a direct result of its structure and of the great range of rock formations which are exposed within a distance of little over twenty miles, for, excepting only the Ordovician and the Permian, there are outcrops of every main group of rocks from the Cambrian to the Chalk.

Just as England affords more variety in its small area than almost any other country, so this district holds in still smaller miniature many of the chief features of English scenery. Its villages show such variety of building stones that it would almost be possible to make a geological map of the area merely by noting the materials used in the cottages. Many of the tall-towered churches are built of oolite, though others take their colour from the local stones.

The best viewpoint within the district is Dundry Hill, a few miles south of the city of Bristol. This hill is a great outlier of the oolite limestones; its slopes are occupied by Lias clays, but the summit is capped by oolitic limestones, which have been quarried for its cottages which nestle beneath it and in the church which forms such a prominent landmark. From the northern face of this hill a splendid view of Bristol and the areas east and west of the city is obtained. The even-topped upland of Durdham Down and Clifton is cut by the narrow gorge of the Avon and stretches thence westwards in a wooded ridge to Clevedon. From the south side of the hill there is a still wider view of open agricultural country backed by the smooth lines of the Mendip range.

Perhaps the most significant feature in the area is the regularity of its hill surfaces, for in any extensive view, large areas appear to be flat-topped, whatever their height may be. There are great stretches of country at more or less uniform levels ; these are cut by valleys and evidently represent low plateaux in various stages of dissection. But apart from this simplicity of many of its outlines the Bristol district has an astonishing complexity of pattern. Ridges run in almost every direction and rivers seem to flow alternately in wide open valleys and in narrow gorges.

To the south of the Mendips lie the ecologically important Somerset Levels, one of Europe's most important wetlands. This area, often referred to as the Plain of Sedgemoor, is a low-lying landscape of willow edged quiet streams which drain into the rivers Parrett and Brue, which, in turn, flow into the Bristol Channel. The maze of drainage ditches, or Rhines, criss-crossing the Levels do not make for easy walking, but running through the centre of this region are the Polden Hills; although these are never more than 300ft high, they provide the means to walk and explore this area and provide good views across the Levels to the north and south. The few islands which rise out of these marshes are thus unusually conspicuous, and have been especially attractive to settlements since earliest times. The most famous among them is the lovely Isle of Avalon with the town and ruins of Glastonbury. This rises to a lofty Tor from which the most wonderful view of these fens is to be had. Further west Brent Knoll has an even greater isolation, overlooking the coast from Brean Down to Burnham and beyond.

Broadly the study area defines the modern county of Somerset and its immediate surroundings (Fig 1).