In China, rammed earth walls were built by the Longshan people in 2600–1900 BC, during the period when cities first appeared in the region. Thick sloping walls made of rammed earth became a characteristic of traditional Buddhist monasteries throughout the Himalayas and became very common in northern Indian areas such as Sikkim. The technique spread to the Middle East, and to North Africa, and the city of Carthage was built of rammed earth. From there the technology was brought to Europe by the Romans.