When Mr Wm Patrick Cranley and his family moved to Shanghai in 1997, they fell in love with the city's early 20th-century buildings.
Their quest for stories about the long-neglected beauties led them to establish an informal study group, Historic Shanghai, in 1998.
Since then, Mr Cranley and his wife, Ms Tina Kanagaratnam (both fluent Mandarin speakers), have become experts in Shanghai's Art Deco era, which lasted from the post-World War I building boom in the 1920s to the mid-1940s.
They lead walking tours, give lectures and organised this year's World Congress on Art Deco held in Shanghai last month.
Shanghai is, "by far", the most well-preserved major city in China, says Mr Cranley, 55, a native of Baltimore in the United States. Since many of its notable Art Deco-era structures were built as hotels, apartment buildings and private homes, they have mostly avoided the wrecking ball.
The range of styles is also noteworthy, he said, because of the many international architects who worked in 1930s Shanghai alongside Chinese architects who had studied abroad. Both groups had encountered Art Deco in the West and discovered that it suited the city perfectly, with its infatuation with progress, innovation and modernity.
Here are edited excerpts from a conversation with Mr Cranley.
What is unique about Art Deco in Shanghai?
It often includes traditional Chinese features such as upturned eaves and lattice windows.
During the early 20th century, the Chinese sought to forge a new national identity, both modern and Chinese, and that is what really defines Chinese Art Deco.
Where should travellers stay in Shanghai and what should they do if they want to revisit the Art Deco era?
Shanghai's 21st-century economic boom has meant a flurry of renovation and not all of it sympathetic. Two good options are the Fairmont Peace Hotel and the Pei Mansion.
Shanghai is a great walking city: safe, reasonably compact and packed with cafes. The former French Concession has the highest concentration of Art Deco architecture. Join one of Historic Shanghai's guided tours or get a copy of Still More Shanghai Walks by Tess Johnston.
Your favourite neighbourhood for architecture?
How do you pick just one? The 1930s Shanghai Municipal Government buildings in the Jiangwan area of Yangpu District are excellent examples of the Ming Revival subgenre of Chinese Art Deco.
The Western part of the French Concession has dozens of Art Deco apartment buildings, each with its own charm and interesting history.
And, of course, the Bund is happy hunting ground for examples of commercial buildings with that unmistakable Art Deco rhythm.
Which is your favourite recent building in Shanghai and why?
While my wife likes the Jin Mao Tower for its combination of Chinese pagoda architecture and Art Deco skyscraper design, I would never choose a recent building over an exquisite historic design.
That said, I am partial to the new Shanghai Tower - not because it is the second-tallest building in the world, but because its simple curves make a massive structure approachable and because it incorporates several eco-friendly innovations.
Do you see any parallels between Shanghai's go-go Art Deco era and today?
Sure. There was a lot of money sloshing around in Shanghai in the 1930s, just as there is today.
And now, architects are searching for a new design vocabulary to express the spirit of the times, as they did back in the Art Deco period. The difference is, in those days, they succeeded.
NEW YORK TIMES