Already well established by the 13th century, the port of Hội An, located at the mouth of the Thu Bồn River, subsequently became an important commercial centre for the wider region. Merchant ships from Japan and China visited the town with increasing frequency, leading to the construction of streets belonging to the merchant guilds and the establishment of distinct Japanese and Chinese quarters with their own architectural styles. During the 17th and 18th centuries it was the busiest of Đại Việt’s four chief commercial ports, the others being Kẻ Chợ and Phố Hiến in the north and nearby Đà Nẵng in the south. Affected by serious silting problems, the port itself went into decline in the face of competition from Đà Nẵng during the 19th century, but many of the buildings erected by rich merchant families during its heyday have been preserved and today these stand as excellent examples of civic architecture. The Hội An Centre for Monuments Management and Preservation is responsible for the restoration and upkeep of the historic buildings in Hội An, which were collectively listed by UNESCO as a World Heritage Site in 1999. In 2000 Hội An won an Honourable Mention in the UNESCO Asia Pacific Heritage Awards for Culture Heritage Conservation. Important vestiges include the following: