This is the heart of ancient Anuradhapura and the focus of religious observances, which draw masses of people dressed in their finest. Relics here date from the 3rd century BC to the 11th century AD.
For the sheer delight of exploring an ancient city, much of it still enveloped in tropical forest, the 2000-year-old Abhayagiri Monastery area can't be beat. Head off the main trails and your only companions will be strutting egrets and the occasional dog-sized monitor lizard.
A map at the entrance shows how the forest surrounding the main dagoba was home to four main mula (colleges or faculties), each with its own residences, refectories, meditation centres and bodhi-tree shrines. An estimated 5000 monks lived here at its peak.
Despite dating from a later period than most of the Buddhist constructions, time has not been kind to the Citadel. Its once-great walls have almost entirely been reabsorbed by the earth, offering a fine Buddhist lesson in the nature of impermanence.
The huge Jetavanarama Dagoba dominates the eastern part of Anuradhapura.
South and west of the main historic and sacred areas are several important and enigmatic sites.
Anuradhapura has three great artificial water tanks, commissioned by the city's kings to provide water for irrigation and to raise tax revenue for the Buddhist community.
Nuwara Wewa, on the east side of the city, is the largest, covering about 12 sq km. It was built around 20 BC and is well away from most of the old city. The northwestern corner offers spectacular sunset views of the old city.
The 160-hectare Tissa Wewa is the southern tank in the old city and is encircled by a dirt road. It's easily accessed from the behind the Isurumuniya Vihara or Royal Pleasure Gardens.
The oldest tank, probably dating from around the 4th century BC, is the 120-hectare Basawak Kulama to the north.
All are good for quiet bike rides and walks along the shorelines.