Xiadu was the lower capital of Yan

Yan (state)

Yān was a state during the Western Zhou, Spring and Autumn and Warring States Periods of Chinese history. Its capital was Ji...

 during the Warring States Period

Warring States Period

The Warring States Period , also known as the Era of Warring States, or the Warring Kingdoms period, covers the Iron Age period from about 475 BC to the reunification of China under the Qin Dynasty in 221 BC...

. The remains of the city are located in Yixian County

Yi County, Hebei

Yi County is a county in Hebei province of China, administratively under the jurisdiction of the prefecture-level city of Baoding. It has an area of ??? km².-Administrative divisions:Towns:...

, Baoding City

Baoding

-Administrative divisions:Baoding prefecture-level city consists of 3 municipal districts, 4 county-level cities, 18 counties:-Demographics:The Baoding urban area has a population of around 1,006,000 . The population of the Baoding administrative area is 10,890,000. The considerable majority are...

, Hebei

Hebei

' is a province of the People's Republic of China in the North China region. Its one-character abbreviation is "" , named after Ji Province, a Han Dynasty province that included what is now southern Hebei...

, China. At 30 km², Xiadu is the largest excavated city from the Warring States Period.

Xiadu was surrounded by a moat

Moat

A moat is a deep, broad ditch, either dry or filled with water, that surrounds a castle, other building or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices...

 and rammed earth

Rammed earth

Rammed earth, also known as taipa , tapial , and pisé , is a technique for building walls using the raw materials of earth, chalk, lime and gravel. It is an ancient building method that has seen a revival in recent years as people seek more sustainable building materials and natural building methods...

 wall; the base of the city walls measured 40 m at its widest. A portion of the old city wall, measuring up to 6.8 m high, still remains today.

The city was flanked by the Beiyi River to its north and by the Zhongyi River to its south. A wall and canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

 ran north-south through the middle of the city, dividing the city into an eastern and western city. Large workshops for casting iron, casting bronze, minting coins, making weapons, making pottery and making bone objects were all found in the eastern city. The palace and royal cemeteries were also located in the eastern city. Two cemeteries were discovered; 13 and 10 tombs were found in each. All the tombs were covered by a tumulus

Tumulus

A tumulus is a mound of earth and stones raised over a grave or graves. Tumuli are also known as barrows, burial mounds, Hügelgrab or kurgans, and can be found throughout much of the world. A tumulus composed largely or entirely of stones is usually referred to as a cairn...

. A museum about the objects found was in Beijing.