SHANGHAI - 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.

Related readings:  Sierra Leone National Pavilion Day celebrated at Expo  Armless?embroiderer heads to Expo for exhibition  National Pavilion Day of Israel celebrated at Expo  Titoni makes time for Expo

"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.

"The Suzhou Pavilion's theme is protecting and making use of historical and cultural heritage," said Tang Zilai, chief designer of the Suzhou Pavilion.

"The city of Suzhou has proved that if the old town is preserved well, it can be a competitive edge for the city. The development of the old town brings opportunities for the new city, " he added.

Other cases at BUPA show artists' designs and how the construction of a landmark building can be the Midas touch for a city's development when it is stranded between the old and the new.

For instance, in 1991, the municipal government of the Spanish city Bilbao decided to build a modern art museum to revitalize its tourism industry.

The completion of the titanium-covered Guggenheim Museum, hailed by many as a highly creative construction, inspired people to be creative and enabled the city to reinvigorate its economy.

There are other examples at BUPA showing how city designers' crave a combination of old and new. In fact, the planning and construction of many projects at the BUPA are exemplary cases of the old being made into the new.

The most eye-catching and symbolic construction at BUPA is a 165-meter chimney-turned-"Expo Thermometer" on the Huangpu River.

The tall chimney from Shanghai's century-old power plant in Puxi is now the tallest structure at the Expo site. Atop it sits a LED screen with a thermometer displaying the temperature.

Connected to the Shanghai Meteorological Bureau, the "Expo Thermometer" updates to give a precise weather forecast every hour.

In 1896 the Nanshi Power Plant on the Huangpu River powered 30 electric bulbs to make Shanghai an "ever-bright city."

Yet 108 years later, workshops at the power plant's former site, now park area for the expo site, have been transformed into shiny and clean exhibition halls.

The transformation of the chimney and utilization of the power plant showcases the recycling of the old city to upgrade the modern city, according to BUPA deputy head Yu Li.