CHALLIS, the chief town of the island of Euboea in Greece, is situated on the strait of the Euripus at its narrowest point. Ancient Chalcis was peopled by Ionians, and early developed great industrial and colonizing activity. In the 7th and 8th cen turies it founded thirty townships on the peninsula of Chalcidice, and several important cities in Sicily (q.v.). Its metalwork, purple and pottery found markets among these settlements, and were distributed widely in the ships of its allies Corinth and Samos. In the so-called Lelantine War, Chalcis won from its neighbour and rival Eretria the best agricultural district of Euboea and became the chief city of the island. But its prosperity was broken by disastrous wars with the Athenians, and it became a member of both the Delian Leagues. In the Hellenistic period it was one of the fortresses by which Macedon controlled Greece. Antiochus III. of Syria (192) and Mithradates VI. of Pontus (88) used it as a base for invading Greece. Under Roman rule Chalcis retained some commercial prosperity; after the 6th cen tury A.D. it again served to protect central Greece against northern invaders. From 1209 it was under Venetian control; in 1470 it passed to the Ottoman Turks, who made it the seat of a pasha. In 1688 it was successfully held against Venetian attack. The modern town has considerable export trade and railway con nection with Athens and Peiraeus (1904). The old walled Castro, towards the Euripus, is inhabited by Jewish and Turkish families; the modern suburb outside it, by Greeks. A part of the Castro was destroyed by the earthquake of 1894 ; part, the famous "Black Bridge," which gave its mediaeval name "Negroponte" to Euboea, has been replaced by a modern swing bridge in the widening of the Euripus. The church of St. Paraskeve, once the chief church of the Venetians, dates from the Byzantine period, though many of its details are Western. The Turkish mosque is now a guard-house.