Coombe Bisset Down Nature Reserve encloses a 0.9 mile-long section of a narrow, dry valley, on the north edge of an extensive chalk upland region on the south side of the River Ebble. There are over a dozen such valleys over a distance of about 13 miles, and the sides of most have historically not been ploughed or otherwise much used for agriculture owing to the steep gradient, so have retained a good selection of calcareous grassland wildflowers. One other valley also part of a nature reserve is Middleton Down, a little way west.
The reserve includes flat land on the valley floor and eastern rim as well as the steep east slope. Some of the more level areas were previously used to grow crops but have since been restored to a natural condition. All sections are periodically grazed, by sheep and cattle, in order to limit the growth of the more vigorous grasses and so create conditions that help more delicate wildflowers to flourish. Hedges and fences allow individual sections to be grazed separately. There are no rock outcrops in the valley, and no single location particularly outstanding for wildflowers, but the best selections seem to be found across the steepest slopes, and the peak blooming time is from late May to the end of June.
The reserve is currently 88 acres in size, all grassland apart from a few narrow patches of trees, the most extensive along the western boundary, though negotiations are in progress to double the area, by purchase of the adjacent, higher land to the west. The main entrance is at the north end, along a little-used country lane (Pennings Drove), just south of Coombe Bissett village and 4 miles from the centre of Salisbury; a gravel parking area accommodates about six vehicles. From here two tracks head south into the meadows, one mostly along the valley floor, the other a little way up the slopes to the east. A third path follows the higher land along the eastern edge, this the main habitat restoration area, where wildflowers are more limited. The slopes are dotted with a few ancient anthill mounds, sustaining their own little selection of flowers. The wider views, over the neighbouring valleys and hills, are quite good though not spectacular.