Sofia (50), capital since 1878 of Bulgaria; is a fortified town, situated in the broad valley of the Isker, a tributary of the Danube, 75 m. NW. of Philippopolis; has recently largely undergone reconstruction, and with hotels, banks, a government palace, &c., presents a fine modern appearance; has a national university; is an important trade emporium, and is on the Constantinople and Belgrade railway; manufactures cloth, silks, leather, &c., and has long been famed for its hot mineral springs.