At the Shanghai Expo's Barcelona Pavilion in the Best Urban Practice Area, images of Barcelona's past and present are projected onto big mirrors. They show how the city's "old town" was preserved even as city expanded.

"The city of Barcelona is an exemplary model showing a harmonious existence between new city areas and old ones," Ye Zhenzhen, a Chinese staffer working at Barcelona Pavilion, said.

City designers in Barcelona are not alone in trying to embrace modern development while preserving the city's heritage.

Through the many exhibits and replica models on display at the expo park, the exhibition cities at BUPA raised a question: Will the lifestyle and relics of the old town be treasured even as modern cities develop?

Barcelona provides a good answer.

The buildings at the heart of the city's old town - some of which are world-renowned Gothic-architecture structures - were rebuilt and had their functionality extended into becoming public facilities like libraries and bars.

The layout of parts of the old streets remain untouched at the old town of Barcelona, which has turned into a popular place for urban residents to relax.

The Chinese city of Suzhou, about two hours' drive from Shanghai, offers another solution: Building a new town out of the old one.

The southeastern Chinese city - famous for its grey-brick houses, beautiful stone bridges, and meticulously designed gardens - built its old town transportation network and water supplies and new city zones as two separate spider webs.

Suzhou City's designers wanted to make sure the two city zones were well connected by transportation, but also wanted to ensure the casual lifestyles in the old city zone could remain.