Gandhāra is the name of an ancient kingdom in northern Pakistan and eastern Afghanistan. This Kingdom lasted from early 1st millennium BC to the 11th century AD. It attained its height from the 1st century to the 5th century under the Buddhist Kushan Kings. Gandhāra is known for the distinctive Gandhāra style of Buddhist art, which developed out of a merger of Greek, Syrian, Persian, and Indian artistic influence. This development began during the Parthian Period (50 BC – AD 75). Gandhāran style flourished and achieved its peak during the Kushan period, from the 1st to the 5th century. It declined and suffered destruction after invasion of the White Huns in the 5th century.
By the time Gandhara had been absorbed into the empire of Mahmud of Ghazni, around 1000 AD, Buddhist buildings were already in ruins and Gandhara art had been forgotten. In the 19th century, British soldiers and administrators started taking interest in the ancient history of the Indian Subcontinent. In the 1830s very old coins were discovered and decipherment of some Chinese records provided locations of Buddhists shrines. Along with the discovery of coins, these records provided necessary clues to piece together the history of Gandhara. In 1848 Gandhara sculptures have been discovered north of Peshawar. From then on a large number of Buddhist statues have been discovered in the Peshawar valley.
See all details at http://en.wikipedia.org/wiki/Gandhara
Headless Standing Buddha, II Century AD, Museo Arte orientale, Torino