One of the outstanding natural features of the South African vineyard and wine landscapes is the distinctive and diverse topography, characterised by magnificent sandstone mountains often resting on granitic foothill bases which merge into undulating shale substrata hills. Closely linked to geology, topography forms an important part of the terroir concept and has a strong interaction with the environmental components of climate and soil. Its effect, both below and above the ground, is considered to be one of the major factors when it comes to the quality of the grapes, with altitude, aspect and inclination of the slope the three most important attributes affecting viticulture. Topographic effects can be indirect, due to soil types, exposure to wind and ventilation, or direct, due to the immediate effects of the incidence of the sun's rays on the earth's surface.
The vineyards of the Cape are planted in a wide variety of locations - hugging valley floors, clambering over hills, climbing steep mountain slopes or tucked beneath high peaks. This varied terrain offers not only a wide range of locations but also many different mesoclimates and soils in which to grow the various cultivars. With increased knowledge of the vine' needs, many farmers have extended their plantings upwards to benefit from better drainage and cooler temperatures. Vineyards may be located from a mere 50 m above sea level to over 600 m in the mountains. A vast difference in height above sea level between the lowest altitude vineyards and the highest can often be found on one single farm. This is often used to differentiate between styles for the same cultivar or to plant different cultivars with different climate requirements on the same farm.
When it comes to aspect, in the southern hemisphere preference is given to the cooler southern and eastern slopes, especially for the more delicate varieties like Sauvignon blanc and Pinot noir. Changes in altitude result in different slopes and aspects with resulting changes in solar radiation interception, temperature and wind exposure. Northern and western slopes are warmer than southern and eastern due to their higher inception of sunlight. Eastern slopes will, however, warm up faster than western slopes and cool earlier.
During the summer months, the sun rises late and sets early behind the peaks in the prime wine-producing vineyards in the mountainous terrain of the Cape, casting deep shadows over the vineyards on the mountain slopes in the early morning and late afternoon, and thus restricting the amount of sunlight hours. Some vineyards only see the sun rising as late as 10:00 in the morning. On the longest day of the year in mid-summer the prime Cape vineyards seldom receive a maximum of more than 10 hours of sunlight.