a 45 m wide and 6.6 m deep moat around the city. According to F. R. Allchin and George Erdosy, these city defences were constructed between 6th and 4th centuries BCE. Dieter Schlingloff believes that these were built before 600 BCE. This period is characterised by structures made of stone and burnt-brick, tools and weapons made of iron, and black and red burnished ware. According to the Puranic texts, a branch of the legendary Haihaya dynasty ruled over Ujjain. Ancient period In the 4th century BCE, the Mauryan emperor Chandragupta annexed Avanti to his empire. The edicts of his grandson Ashoka mention four provinces of the Mauryan empire, of which Ujjain was the capital of the Western province. During the reign of his father Bindusara, Ashoka served as the viceroy of Ujjain, which highlights the importance of the town. As the viceroy of Ujjain, Ashoka married Devi, the daughter of a merchant from Vedisagiri (Vidisha). According to the Sinhalese Buddhist tradition, their children Mahendra and Sanghamitra, who preached Buddhism in modern Sri Lanka, were born in Ujjain. From the Mauryan period, Northern Black Polished Ware, copper coins, terracotta ring wells and ivory seals with Brahmi text have been excavated at Ujjain. Ujjain emerged as an important commercial centre, partially because it lay on the trade route connecting north India to the Deccan, starting from Mathura. It also emerged as an important center for intellectual learning among Jain, Buddhist and Hindu traditions. After the Mauryans, Ujjain was controlled by a number of empires and dynasties, including local dynasties, the Shungas, the Western Satraps, the Satavahanas, and the Guptas. Ujjain remained as an important city of the Guptas during the 4th and the 5th centuries. Kalidasa, the great Indian classical poet of the 5th century who lived in the times of the Gupta king Vikramaditya wrote his epic work Meghadūta in which he describes the richness of Ujjain and its people. In the 6th century CE the Chinese pilgrim Xuanzang visited India. He describes the ruler of Avanti as a king who was generous to the poor and presented them with gifts. Bharthari is said to have written his great epics, Virat Katha, Neeti Sataka, the love story of Pradyot Princess Vasavadatta and Udayan in Ujjayini, as the city was called during his times. The writings of Bhasa are set in Ujjain, and he probably lived in the city. Kalidasa also refers