It lies in the most dry part of the dry zone of Central Burma, so during the dry season, the mighty Irrawaddy is nothing but a small creek. The river was a quite disappointing site when I was there.
Pagan (or Bagan) briefly became the capital in 847 AD. But it was not until from 1057 that Pagan became great. That year was when Pagan became the capital of the first "real" (i. e., united) Burmese kingdom. King Anawrahta, consolidated political and military power over all of Central Burma by conquering both the Pyu and the Mon peoples.
After Anawrahta conquered Thaton (the Mon kingdom), he brought back to his capital the Theravada scriptures in Pali, a large number of Buddhist monks, and artists and craftsmen of every description. From the Mon monks, the Pagan people received their alphabet, religion and scriptures. Moreover, an extraordinary architectural and artistic activity began. In a little more than two centuries, he covered the city and its environs with thousands of splendid monuments of every shape and size
The square temples dominated by Mon influence are distinguished by their dark corridors, which are dimly lighted by perforated windows, and by the bright frescoes with Mon writing on the walls. The typical Pagan Style temples are bright and airy within, with imposing plan and height. But there are also some temples with intermediate forms.
It all ended in1287. The Pagan kingdom fell to the Mongols, after refusing to pay tribute to Kublai Khan. Abandoned by the Burmese kings, the city declined as a political centre, but continued to flourish as a place of Buddhist scholarship.
Up to around 5,000 monuments or buildings were constructed although "only" 2,200 remain (in more or less dilapidated state) within the 40-50 square kilometer area.
What I really liked about Pagan (back when I visited) was that it was very low key, very untouristed.
I stayed in a nice little hotel with rooftop restaurant from where I could have breakfast while enjoying the view of stupas and ruins. After breakfast, I made my way around the area at a leisurely pace on my rented bicycle.