Yemen's chief port is ADEN, which is a four-letter word. ADEN is a seaport city in Yemen located on the Gulf of ADEN by the eastern approach to the Red Sea. It is the economic and administrative center of Yemen, and is the second largest city in the country after the capital Sana'a. ADEN is an important commercial hub for the region, and serves as a key refueling and transshipment center. It is also home to a large oil refinery and a free trade zone.