(anc. Sena Julia), a town of Tuscany, capital of a province of the same name, in a barren and dreary plain, 31 miles S.E. of Florence. The immediate vicinity, however, is well planted with trees, and thus the town presents a very fine appearance, as it is approached through fine shady avenues. It stands on the declivities of two hills, and its streets are in consequence in many places very steep, so as to be impassable for carriages. They are also narrow and irregular, generally paved with tiles, and the town has so much declined in importance that many of the streets are quite desolate and overgrown with grass. The houses are for the most part built of brick, and frequently bear the imposing appellation of palaces. But the principal buildings are the churches, foremost among which comes the cathedral. This edifice, built in the eleventh, twelfth, and thirteenth centuries, is one of the most characteristic examples of the Italian Gothic architecture; though producing a somewhat disagreeable effect from the incongruity of its different parts, and the profusion of coloured marble with which it is adorned. In the interior are several good paintings and carvings, a curious inlaid pavement, and a beautiful marble pulpit, the work of Nicolò de Pisá. Several of the other churches contain valuable paintings. The principal public place, the Piazza del Campo, is of a semicircular form, about 1000 feet in circuit, and has a general slope towards one end. Here stands the Loggia di San Paolo, celebrated in the middle ages as the seat of a commercial tribunal; and the Palazzo Pubblico, with a lofty tower. This building was begun in 1295, and completed in 1327; it now contains the public offices, law-courts, and prisons of the town. The other palaces of Siena exhibit fine specimens of medieval domestic architecture in all varieties of Gothic style. The university, founded in 1203, has greatly declined from its ancient prosperity. It has a library of about 40,000 volumes, and 5000 manuscripts, some of which are of great value. Among the other public buildings of Siena, are an hospital, a citadel with five bastions, several schools, &c. There are several handsome fountains in the town, and some of the gates are very beautiful. Some manufactures are carried on here, the chief productions being woollen cloth, hats, paper, and leather; and there is some trade in corn and marble. The people of Siena boast of the purity of their pronunciation and accent; and they certainly excel in this respect those of Florence, though retaining some of the harshness of the Tuscan dialect. This town was in the middle ages one of the most celebrated and powerful republics of Italy, and played an important part in the history of these times, when it was the rival of Florence. As the latter city belonged to the Guelph party in the contest between the emperor and the pope, while Siena maintained the Ghibelline cause, or that of the emperor, frequent wars took place between the two cities. In 1258, Farinata degli Uberti, who had been expelled from Florence by the Guelphs, took the command of the troops of Siena, and gained a complete victory over his adversaries at Monte Aperto. At a subsequent period Siena extended its dominions as far as the sea; but it never became a naval power of any importance. During the latter half of the fourteenth century, vehement dissensions took place between an aristocratic and a reforming party in the state, which ended in 1384 in the expulsion of several thousands of the latter. Peace, however, was not restored, either by this victory or by the efforts of Pope Pius II., who visited the town in 1460; civil discords continued to rage, and in 1482 a new revolution took place, and the old popular party was recalled. The government now became more democratic, but not less turbulent or factious than it had formerly been. For a time the ambition and ability of Pandolfo Petrucci raised him to be virtually dictator of Siena, and the republican form of government was enabled to survive that of Florence by the protection of Charles V.; but the people subsequently expelled the Spanish garrison. Finally, in 1555, the town had to succumb to the arms of Spain, by whom it was handed over to Duke Cosmo of Florence. Since that time it has belonged to the Grand Duchy of Tuscany. Its population at the height of its prosperity was 100,000, but in 1855 was only 25,435.

SIERRA in Spanish, and Serra in Portuguese, names literally signifying a saw, but applied in geography to numerous mountain-ridges, both in the old and new world. (See Spain, Portugal, Mexico, Brazil, &c.)