Eight-year-old Emily, from New York, hopes everyone rides a bike; 10-year-old Tyler, from Johannesburg, South Africa, hopes he can walk to school; five-year-old Bastet, from Cairo, Egypt, hopes the city smells very nice.

All the kids were responding to a question: "What would be different in the city of your dreams?"

Coming from all corners of the globe, they gave the above answers at the Urban Planet Pavilion, one of the five themed pavilions at the Shanghai Expo park.

All the cities they live in face the pressures of population growth, resource strain, climate change, and environmental pollution.

Over half of the world's population live in cities, and that will be three quarters by 2050, according to the United Nations.

"People should restrain from exploiting the earth's natural resources too much. And they should stop sabotaging the environment," commented China Telecom employee Cheng Zhuo after he visited the pavilion.

"The cities should resort to low-carbon and clean models for future development," he said.

It took millions of years to turn biomass into coal and oil, natural gas and peat. But in just the last century, humans have burned up more of it than they did in the previous millennium.

As Carmen Bueno, designer of the Pavilion of the Future, said: "The urban future is derived from the present."

As the first Expo to feature the theme 'City,' the Shanghai World Expo, which opened to the public Saturday, is a platform for visitors to understand cities as a source of some of the world's problems and their solutions.

"The Expo has alerted us to environmental protection, and it inspires us to work out more reasonable plans for the cities of the future," said 86-year-old expo-visitor Zheng Jiwen.

"What people need to do is to live a green, fresh and eco-friendly life," he said.

The Urban Planet Pavilion shows how cities' development -- sometimes overdevelopment -- creates ecological problems, and how people have responded to urbanization and environmental challenges.

Designers have proposed to develop a green urban-transport vehicle, a bubble-shaped car powered by the solar panels mounted on its roof.

At night, the cars are stored atop telescopic poles, on which they act as street lights while keeping the ground free of parked vehicles.

A British scientist wants to sail hundreds of ghost ships - called "spray robots" - on the world's oceans to constantly blow seawater into the air to help stop global warming.

The answers to questions about how cities and the earth can coexist are not only in the Urban Planet Pavilion. They lie in every corner of the Expo park, which has translated them into different ideas, technologies and research.

Straddling the Huangpu River, the Expo park is expected to draw 70 million visitors over the six months it runs.

On the river's eastern bank, giant white funnels provide shade and channel sunlight to underground walkways while collecting rainwater for recycling.

On the west bank, an array of pavilions showcase urban best practice and highlight sustainable technologies and heritage preservation.

Stepping out of one themed pavilion, Qin Le, a 9-year-old boy from Shanghai, said: "I will travel by buses more frequently from now and walk if I can, instead of using a car. This will cut carbon dioxide emissions."

"In the city of my dreams, all vehicles will be powered by solar panels and have zero-emission," the boy said.