of not writing it down so that even if some of the monks whose duty it was to study and remember parts of the Canon for later generations died, the teachings would not be lost. After the council, palm-leaf manuscripts containing the completed Canon were taken to other countries such as Burma, Thailand, Cambodia and Laos. Sri Lanka was the first Asian country known to have a female ruler: Anula of Anuradhapura (r. 47–42 BCE). Sri Lankan monarchs undertook some remarkable construction projects such as Sigiriya, the so-called "Fortress in the Sky", built during the reign of Kashyapa I of Anuradhapura, who ruled between 477 and 495. The Sigiriya rock fortress is surrounded by an extensive network of ramparts and moats. Inside this protective enclosure were gardens, ponds, pavilions, palaces and other structures. In 993 CE, the invasion of Chola emperor Rajaraja I forced the then Sinhalese ruler Mahinda V to flee to the southern part of Sri Lanka. Taking advantage of this situation, Rajendra I, son of Rajaraja I, launched a large invasion in 1017. Mahinda V was captured and taken to India, and the Cholas sacked the city of Anuradhapura causing the fall of Anuradhapura Kingdom. Subsequently, they moved the capital to Polonnaruwa. Post-classical Sri Lanka Following a 17-year-long campaign, Vijayabahu I successfully drove the Chola out of Sri Lanka in 1070, reuniting the country for the first time in over a century. Upon his request, ordained monks were sent from Burma to Sri Lanka to re-establish Buddhism, which had almost disappeared from the country during the Chola reign. During the medieval period, Sri Lanka was divided into three sub-territories, namely, Ruhunu, Pihiti and Maya. Sri Lanka's irrigation system was extensively expanded during the reign of Parākramabāhu the Great (1153–1186). This period is considered as a time when Sri Lanka was at the height of its power. He built 1,470 reservoirs – the highest number by any ruler in Sri Lanka's history – repaired 165 dams, 3,910 canals, 163 major reservoirs, and 2,376 mini-reservoirs. His most famous construction is the Parakrama Samudra, the largest irrigation project of medieval Sri Lanka. Parākramabāhu's reign is memorable for two major campaigns – in the south of India as part of a Pandyan war of succession, and a punitive strike against the kings of Ramanna (Burma) for various perceived insults to Sri Lanka. After his demise, Sri Lanka gradually decayed in power.