In the Middle Ages, it was an important port for Java's foreign trade. Surabaya is the most industrialized industrial and commercial city in Indonesia. A large part of Indonesian imports enter China through this port, while most of the exported sugar, coffee, tobacco, teak, cassava, rubber, spices, vegetable oil and petroleum products are also exported through this port. Industries include docks, railway locomotive manufacturing, textiles, glass, chemicals, beer brewing, cigarettes and shoemaking. There is an international airport. Surabaya has a huge fishing fleet, and the city is surrounded by rich agricultural areas. The city has good railway, highway and air links with towns in Java. Famous buildings include the Grand Mosque built in 1868, Erlangka University built in 1954, Polytechnic Institute, Naval Academy and a Dutch castle. On September 2, 2003, Guangzhou established cooperation and exchange relations with Surabaya, China.