AS WE SIT IN YANGON peak-hour traffic, Thant Myint-U is conjuring a golden age. The eminent Burmese historian, academic and former United Nations official has devoted much of the last two years to saving the city's spectacular architecture. Despite the gridlock as we slowly nudge through its colonial heart, we couldn't be better placed to recall the glories of old Rangoon (as Yangon was once known). It's difficult to remember today, thanks to nearly five decades of Myanmar's political isolation under brutal military rule, but there was a time when it was one of the jewels of the British Empire.

In the 1920s, travelers from all over the world would arrive by ocean liner at the palm-fringed harbor, then plunge wide-eyed into the cosmopolitan avenues, where monks with shaved heads rubbed shoulders with English bankers and Scottish engineers and gilded pagodas glinted alongside the splendid façades of imperial buildings. Rangoon was one of the world's most vibrant ports—a key link in the trade route from Calcutta to Shanghai and a place that lured royals, celebrities, artists and adventurers. Nearly everyone of note stayed at the stately Strand hotel—which boasted one of the finest European restaurants in Asia—an enclave of European style founded by the same Armenian family who owned Singapore's Raffles. They would soon join the frenzied expat parties in private clubs, where gallons of champagne were drunk on humid nights scented with tropical flowers and jazz bands played until dawn under the slowly beating fans....