Touraine is a wine district and AOC at the very heart of France's Loire Valley wine region. Its main commercial centre, the city of Tours, sits precisely half-way between Sancerre and Nantes (the home of Muscadet).

Touraine has its own generic regional appellation. This covers the entire district with around 5000 hectares (12,350 acres) of designated vineyards.

Wines made under the Touraine regional appellation may be white, red, rosé or sparkling (in all three colours). Whites account for 59 percent of production, reds for 22, rosé for eight and sparkling 11 percent.

The white wines are most commonly based on Sauvignon Blanc, which accounts for 43 percent of all Touraine plantings. Chenin Blanc comes a distant second at 7 percent. Chardonnay is allowed to form up to 20 percent of blends, and accounts for 3 percent of vineyard area.

A little Arbois (or Orbois) is also grown here – it was once the most common variety in the Loir et Cher département in which part of the Touraine zone lies. Sauvignon Gris is also grown in a few vineyards.

The red grape counterparts are led by Gamay which is planted in 21 percent of Touraine's vineyard area. Cabernet Franc and Malbec (known here as Côt) are also used in red wines, with smaller proportions of Cabernet Sauvignon and Pinot Noir.

Touraine rosés account for about 10 percent of production. They are dry in style. The above grape varieties are used, plus the less-favoured Grolleau Noir and Pineau d'Aunis, and even Pinot Meunier. Pinot Gris can also play a role. There are also several appellations within its borders which are more specific in terms of both location and wine style. These range from the dry, fruity reds of Chinon, Bourgueil and Saint-Nicolas de Bourgueil to the diverse whites of Vouvray and Montlouis. The Cheverny and Cour-Cheverny zones, trapped in the hinterland between the cities of Tours and Orleans, are often grouped into the wider Touraine area on maps and wine lists.

In addition there are five designations within the AOC Touraine where producers may add a geographic suffix. These are Touraine-Amboise, -Chenonceaux, -Mesland, -Oisly, and Touraine Azay-le-Rideau.

The Touraine district follows the Loire river for roughly 100 kilometres (60 miles), from Blois in the east to Chinon and Bourgueil in the west. Beyond this the river continues into the adjacent Anjou district.

It is located around 225 kilometres (140 miles) from the Atlantic Ocean, and the same from the northern Massif Central hills of central France. As a result, the climate here falls somewhere between maritime and continental.

In summer, the slow-moving waters of the Loire do little to cool the Touraine vineyards. The region is known for its hot, torpid summer days. There is, however, a noticeable variation in winter temperatures within Touraine. The district's eastern edge tends to have colder and drier winters. In the west of the region they are usually slightly wetter and more temperate. Throughout the Touraine, the better vineyard sites are those blessed with free-draining soils rich in tuffeau. Tuffeau is the calcareous rock for which this part of the Loire Valley is famous. It was used as the building material for most the valley's famous châteaux. Tuffeau caves also proved perfect for long-term wine storage and ageing.

There are various etymologies and confusions surrounding tuffeau, tuff and tufa, but what is clear is that the rock here in the central Loire is a form of soft, porous limestone formed during the Turonian age (named after Tours) of the Cretaceous period, roughly 90 million years ago.

Its two key forms are chalkier, firmer tuffeau Blanc and softer, sandier tuffeau jaune. The former is used for building châteaux, while the latter underpins the Loire's finest Cabernet Franc vineyards, in Saumur. Both types are geologically distinct from the volcanic rock on which the vineyards of Tufo, southern Italy, are planted (see Greco di Tufo).