Plovdiv is the second most important city. It is older than Sofia, having been established in the fourth century B.C. by Philip of Macedon; it was first named Philippopolis after him. On the plain and astride the route from Belgrade to Istanbul, it has been exposed to all who have passed that way, for good or ill, and this is reflected in its violent history. It has been captured and devastated in turn by Greeks, Romans, Goths, Huns, and Turks. It was also ravished on four different occasions by Christian armies during the Crusades. Plovdiv has continued to be an important commercial city, having more rail lines radiating from it than Sofia. It also has a university and some of the country's most important museums and art treasures. The old town center is typically Macedonian and, although it was severely damaged by an earthquake in 1928, part of it has been termed a national monument, to be reworked only for its restoration. Veliko Turnovo, situated astride a mountain stream on the northern slopes of the central Stara Planina, was the fortress capital of the medieval Second Bulgarian Kingdom. It was also the site of the first constituent assembly held as the country was liberated from the Turks, and the Turnovo Constitution was adopted there in 1879. It remains an artistic and cultural center, and some of its fine examples of Bulgarian renaissance architecture have survived. Varna and Burgas are the chief Black Sea ports, and Ruse is the only major Bulgarian port on the Danube River. Burgas is a young city, growing to most of its size in the late 1800s, and it was a more important port than Varna until the 1950s. Varna, however, attracted the naval academy, has become the naval base, and has acquired most of the shipbuilding industry. Ruse has also grown rapidly. In addition to its river trade, the first bridge across the river between Bulgaria and Romania was built just north of the city. A number of new towns have been built since World War II, in some cases from the ground up. These include some at industrial complexes, others at resorts. Madan is a new mining center in the Rodopi; Dimitrovgrad is a new industrial town on the Maritsa River; and there are several mountain and seaside resort cities. Zlatni Pyassutsi (Golden Sands), opened in 1956, is one of a group of Black Sea resort cities that, upon opening, could accommodate tens of thousands of holiday vacationers. POPULATION Structure