Anuradhapura have uncovered information about the existence of a protohistoric habitation of humans in the citadel. The protohistoric Iron Age which spans from 900 to 600 BC, marked the appearance of iron technology, pottery, the horse, domestic cattle and paddy cultivation. In the time period 700 to 600 BC the settlement in Anuradhapura had grown over an area of at least 50 ha. The city was strategically situated of major ports northwest and northeast, it was surrounded by irrigable and fertile land. The city was also buried deep in the jungle providing natural defence from invaders.The Lower Early Historic period, spanning from 500 to 250 BC, is studied on the lines of the chronicles. During this time King Pandukabhaya formally planned the city, with gates, quarters for traders etc. The city at the time would have covered an area of 1 square kilometre which makes it one of the largest in the continent at the time.The layout of Anuradhapura as described in the Mahavansa:"He laid out four suburbs as well as the Abhaya-tank, the common cemetery, the place of execution, and the chapel of the Queens of the West, the banyan-tree of Vessavana and the Palmyra-palm of the Demon of Maladies, the ground set apart for the Yonas and the house of the Great Sacrifice; all these he laid out near the west gate." Mahavamsa X, trans. Wilhelm Geiger"A hermitage was made for many ascetics; eastward of that same cemetery the ruler built a house for the nigantha Jotiya.(...) On the further side of Jotiya's house and on this side of the Gamani tank he likewise built a monastery for wandering mendicant monks, and a dwelling for the ajivakas and a residence for the brahmans, and in this place and that he built a lying-in shelter and a hall for those recovering from sickness." Mahavamsa X, trans. Wilhelm GeigerIt is said that King Pandukabhaya made it his capital in the 4th century BC, and that he also laid out the town and its suburbs according to a well organized plan. He constructed a reservoir named Abhayavapi. He established shrines for yakkhas such as Kalawela and Cittaraja. He housed the Yaksini-Cetiya in the form of a mare within the royal precincts and offerings were made to all these demi-gods every year. He chose the sites for the cemetery and for the place of execution, the Chapel of the Western Queen, the Pacchimarajini, the Vessavana Banyan Tree, the Palm of the Vyadhadeva, the Yona Quarter and the House of the Great Sacrifice. The slaves or Candalas were assigned their duties and a village was set apart for them. They build dwellings for Niganthas, for wandering ascetics and for Ajivakas and Brahmanas. He established, the village boundaries. The tradition that King Pandukabhaya made Anuradhapura the capital city of Sri Lanka as early as the fourth century BC had been very important.The administrative and sanitary arrangements be made for the city and the shrines he provided indicate that over the years the city developed according to an original master plan. His son Mutasiva, succeeded to the throne. During his reign of sixty years, he maintained Anuradhapura as his capital and further laid out the Mahameghavana Garden which was to play an important role in the early history of Buddhism in Sri Lanka. It was in the period of his successor, his son Devanampiya Tissa, that Buddhism was first introduced this island 236 years after the passing away of the Buddha. Emperor Ashoka in India was a contemporary of Devanampiya Tissa. Historically this period is considered to extend from 250 to 210 BC. This is the point at which a kingship began and a civilization developed based on one of the most significant religions of South Asia, Buddhism.With the introduction of Buddhism, the city gained more prominence and the great building era began. The Mahavansa states that King Kutakannatissa built the first city wall to a height of seven cubits with a moat in front of the wall. This fortification was further enlarged by raising the wall a further 11 cubits to 18 cubits by King Vasabha. The king also added fortified gatehouses at the entrances of which the ruins can be seen to date. The Mahavamsa also states that soothsayers and architects were consulted in the construction.The city's popularity grew both as a ritual centre and as the administrative centre, a large population was attracted to the city for permanent settlement. Thus the living facilities were improved to accommodate the expanding population. King Vasabha constructed many ponds which were fed by a network of subterranean channels which were constructed to supply water to the city. Tissa and Abhayavapi tanks were built, the Nuwara weva was built and the Malwatu Oya was dammed to build the Nachchaduwa wewa which was 4408 acres (17.84 km²) in size.Parks were also provided in the city. The Ranmasu Uyana below the bund of Tissavapi or Tisa weva was one such, but it was strictly reserved for the members of the royal family. Health care and education were two other aspects to which the authorities paid attention. There were several hospitals in the city. In the fourth century King Upatissa II provided quarters and homes for the crippled and the blind. King Buddhadasa (337-365 AD), himself a physician of great repute, appointed a physician to be in charge of every ten villages. For the maintenance of these physicians, one tenth of the income from the fields was set apart. He also set up refuges for the sick in every village. Physicians were also appointed to look after the animals. Kassapa V (914-923 AD) founded a hospital close to the southern gate of Anuradhapura. General Sena in the tenth century is believed to have built a hospital close to the ceremonial street (Managala Veediya). The history of medical care began early, for in the fourth century BC King Pandukhabaya, in the course of sanitizing the town constructed a hospital. A large workforce was entrusted with the task of keeping the city clean.Large lakes were also constructed by the city's rulers to irrigate paddy lands and also to supply water to the city. Nuwara wewa and Tissa wewa are among the best known lakes in the city.Anuradhapura attained its highest magnificence about the commencement of the Christian era. The city had some of the most complex irrigation systems of the ancient world, situated in the dry zone of the country the administration built many tanks to irrigate the land. Most of these tanks still survive.According to carbon dating, the ruins excavated were from the 10th century B.C.The ruins consist of three classes of buildings, dagobas, monastic buildings, and pokunas. The dagobas are bell-shaped masses of masonry, varying from a few feet to over 1100 ft (340 m) in circumference. Some of them contain enough masonry to build a town for twenty-five thousand inhabitants. Remains of the monastic buildings are to be found in every direction in the shape of raised stone platforms, foundations and stone pillars. The most famous is the Brazen Palace erected by King Dutugamunu about 164 BC. The pokunas are bathing-tanks or tanks for the supply of drinking water, which are scattered everywhere through the jungle. The city also contains a sacred Bo-Tree, which is said to date back to the year 245 BC.In the sacred city of Anuradhapura and in the vicinity are a large number of ruins. These have not been identified properly and many have been destroyed either by Tamil invaders or by vandals. Neither the tourists nor the pilgrims had paid much attention to these ruins and information regarding this is meager. Although Avukana is not situated in the sacred city of Anuradhapura, the pilgrims never fail to pay homage to this statue.