With just over 3,000 hectares of vines, the Rheingau is a relatively small wine region and is roughly one eighth of the area of its southerly neighbour Rheinhessen. It has traditionally enjoyed a prestigious reputation and strong demand, due to the quality of its wines, its easy access to market, and its key role in Germany's wine history. It was the first region to develop the 'Prädikat' system of harvesting wines at different ripeness levels (Kabinett, Spätlese and so on) in the 18th Century. Development continues apace at the world-famous Geisenheim Institute, which was founded in the Rheingau back in the 1870s and remains Europe's leading research centre. The Rheingau is reasonably dry, compared with many regions in Germany, and is sheltered by the Taunus mountains lying just above it. However, it is still relatively northerly in latitude and, as might be expected, is predominantly a white wine area that is devoted mainly to Riesling. Only 15% of the total production is red wine, made from the Spätburgunder (Pinot Noir) variety. The vineyards extend from Wiesbaden in the east, down to the River Rhine and west to Lorchausen. From here, the region of Mittelrhein reaches northwest to meet the Mosel. The best vineyards of the Rheingau face due south, on the slopes leading down to the river, and the higher day-time temperatures here result in greater ripeness. The topography and soils differ dramatically along the banks of the river. Slate soils dominate the vineyards west of Rudesheim, while, moving east, the slate soils gradually mix with quartz and then sandier and loess soils. This is the central section of the Rheingau region, where the highest-regarded estates have their home. The eastern section of the Rheingau (around Hochheim) is less steep and has a high limestone content in the soils.