The current name is an abbreviation of its original medieval one: Sant'Agata or Santa Ada. It is a municipality in the province of Carbonia-Iglesias, located in the Sulcis area, on the South-west coast of Sardinia, on the border with the province of Cagliari. The village is located at the center of a valley, not far from a mountain range, of which Monte Tiriccu is part, with its 1104 meters above sea level, and is divided into two districts separated by the Rio Mannu. The main centre Santadi 'and Susu is placed on a higher ground, spread around the Parish Church of San Nicolò. The local economy is mainly based on agriculture and cattle-raising. Of great interest is the Mauritanian Wedding, an special event that takes place every year in August.
The presence of a settlement is proven since ancient times: of particular importance is the site of Su Benatzu, where, in the cave Pirosu, votive ornaments have been found belonging to the Iron Age, and the site of Pani Loriga, which witnesses the presence of Phoenicians and Carthaginians in the area since the VII century B.C. The area was later colonized by the Romans. The foundation of the present settlement dates back to 1066, a period in which the territories belonged to the Parish of Sulcis. In the second half of the XIII century it became a possession of Pisa and in the following century it was granted in fief to Pietro De Sena. Later it became a territory of the Bishop of Sulcis and then passed to Iglesias.
- the XV century Church of St. Nicholas, was restored in the XIX century. It features a one nave plan and barrel vault ceiling. Inside are preserved a Holy Cross of the XVIII century, two silver candlesticks and other valuable items;
- the Church of Madonna delle Grazie, built at the end of the XVI century, features a single nave plan and a belfry;
- the Church of Santa Maria di Monte Flacco;
- the fortress Pani Loriga, located a few kilometers from the main center, an area in which lie the remains of a settlement of the Phoenician era;
- the Cavern of Is Zuddas, interesting from archaeological and speleological points of view;
- the House Museum of Sa Domu Antiga, which is the reconstruction of a typical house of the Sulcis area;
- the Archaeological Museum, which preserves several precious relics;
- the Cavern of Pirosu.