"The Sixth Buddhist Council was inaugurated at Kaba Aye in Yangon (formerly Rangoon, Burma) in 1954, 83 years after the Fifth Council in Mandalay. It was sponsored by the Burmese Government led by the Prime Minister, the Honorable U Nu. He had previously authorized the construction of the Mahā Pāsāna Gūhā, a great artificial cave built from the ground up and completed in 1952, to serve as the gathering place, much like Rajgiri's Sattapānni Cave in India had housed the First Council immediately after the death of the Buddha. This new "cave" measured 220' by 140' inside and could seat 10,000 people..."Note: there have only been 6 councils in the past 2500 years, and a full third of them took place in Burma.
"The complete traditional recitation of the Theravada Canon took two years, from 1954 to 1956. The Pali Tipiṭaka and its allied literature in all the diverse national scripts were painstakingly examined, their differences noted, necessary corrections made, and all the versions collated."
Of course, we all know what's going on there today...
[bonus: photos from the month I spent there in 1/2003]