Professor Jeffrey Shaw says it took three years to build City in Time, from conception to completion.

"That is a City University of Hong Kong School of Creative Media project, commissioned by the Tourism Commission," said Shaw, who holds the Yeung Kin Man Chair Professorship in Media Art.

Shaw coordinates the production team that is made up of School of Creative Media students and working artists.

He told me some graduates came back to help, showing just how challenging and fascinating this venture was.

City in Time is an augmented reality platform that enables its users to relive scenes from Hong Kong's storied past - streets and buildings - at designated locations across the city, and compare them with present-day views.

Artists reinterpreted scenes from old Hong Kong to create this panoramic imagery in 360-degree and three-dimensional models, complete with ambient sounds of traffic and people.

This being an era of apps, you can simply download the City in Time application to enjoy what it has to offer.

The mobile app allows you to use your smartphone camera to compare scenes from the Hong Kong of old with the present-day setting around you.

The web version, meanwhile, compares them to panoramic photographs of the present-day environment.

For an on-site experience, find the eye-catching red augmented reality clock at designated locations (there are 28 so far) and scan it to go back in time to view that same location half a century or even a century ago. You can find out how much Hong Kong has changed.

That brought back memories of Nancy Kwan, the lead actress in the 1960 movie The World of Suzie Wong, a romantic drama that took place in old Hong Kong.

She revisited the territory many years after the screening of the movie, and remarked on the drastic changes she saw.

I shared Kwan's sentiments about how much the territory has changed over the years.

Next time Kwan visits, she may download the City in Time app and visit the Tsim Sha Tsui clock tower, which was the Kowloon terminal of the Kowloon-Canton Railway in Suzie Wong's time.

In trying to recall changes that have happened to our city, in Central, the Peak, Jordan or Yau Ma Tei, where there used to be a cross-harbor ferry pier, our memories may not be totally reliable.

Enlist the help of City in Time as you go down memory lane to view a more accurate picture of change in the cityscape over the decades.

Terence Chang Cheuk-cheung is the retired headmaster of Diocesan Boys School

See change with the City in Time