The best vineyards are on the steep, south-facing slopes overlooking the Mosel river which enjoy the best sun exposure and, to a much smaller extent, sunshine reflected from the river. Steep sites mean expensive vineyards and labour intensive. Soil The dark-coloured slate soil also plays an important part in radiating heat. The slate soils come in a variety of colours – grey, blue, brown and red – and producers are increasingly interested in how subtle differences can influence the characteristics and aromas of their wines