'I was on a site visit when I saw kids holding hands and crossing the river every day.

'The villagers told me they were going to school on the other side although it wasn't safe. They said there had been some accidents before.

'I thought: 'I should build a bridge for them before building a school'.'

With donations from patrons and help from volunteers, the first bridge was completed in 2005. In 2007, Ng set up the Wu Zhi Qiao (Bridge to China) Charitable Foundation and began to build bridges in different places on the mainland.

In Chinese, wu zhi qiao means 'bridges that never end'. 'These are bridges that never end, like love,' Ng says.

So far, 13 bridges have been built in Gansu, Yunnan, Sichuan, Anhui, Guizhou and Shaanxi .

Currently, the foundation is building eight more bridges and working on the 'Sichuan Village Rebuild Demonstration' project with the mainland's Ministry of Housing and Urban-Rural Development.

Ng says it takes about a week and 10 to 80 pairs of hands to build a bridge, depending on its complexity. Fifteen universities from Hong Kong, the mainland and the United States have been involved in the projects. The volunteers included Jayne So Chi-wing and Kenneth Chan Kin-wang, both from CUHK.

'I was very curious about the project. How do we build a bridge?' says So, a postgraduate law student with no architectural background. The 23-year-old has already helped to build two bridges. 'I love the outdoors,' she says with a grin.

Chan, a Year Two architecture student, has been helping with the research.

'We studied the [locations] and found out how many people will be using the bridge after it's built. We also did the technical work like measuring the river banks,' he says. 'I learn so much about architecture in real life ... It is not covered in textbooks.

'It's also great to know the bridge will reduce the farmers' daily trip from six to two hours.'

For So, it has been a life-changing experience. 'I've learned to appreciate what I have - even clean water,' she says.