Last week, I had the privilege of touring the newly refurbished National Gallery before it is opened to the public later this year.

There was a group of us and we had walked there from the nearby Victoria Theatre and Concert Hall, which has also been lovingly restored.

It was just starting to rain so we picked up the pace. As we burst through the doors of the first of two old buildings that make up the Gallery - the former Supreme Court Building - a wave of nostalgia suddenly hit me.

But it wasn't the beauty of the ornate wooden ceilings or the grandeur of the Corinthian columns that triggered the nostalgia, it was - of all things - the tile pattern on the floor.

For those who haven't seen it, it's a simple black and white square grid design with yellow accents - rather severe, but also immediately distinctive.

For a long while, I ignored our museum guide, who was saying something about poisonous asbestos, and just stared silently at the floor beneath my feet. It is just a small detail in the overall restoration of these national monuments, but those tiles brought me right back to 1990.

I was a young man who had just enlisted into national service and had applied for a Public Service Commission (PSC) scholarship. So I went to its offices in City Hall, which was next to the Supreme Court, several times - first for a written psychometric test and subsequently for interviews.

I can't remember now whether I had gone to the Supreme Court by mistake or whether the same floor tile pattern was also in the dark basement entrance foyer of the adjoining City Hall, but it somehow left a deep impression on me.

Perhaps it was the absurdity of having squatted in the dust and mud on Pulau Tekong just hours before. Maybe it was the realisation that a large part of the life that was to come hinged on what was about to transpire in the next hour.

But those tiles made me realise how young I was then and how nervous I felt about my impending adulthood. For a moment, I re-lived that strange mix of terror and excitement I felt as a kid who had never flown on an airplane and was maybe being given a chance to see a world outside the borders of this small country, the only place he had ever known.

I must have stared at the floor a lot as those thoughts raced through my head.

Singapore turns 50 today and, in the run-up to this milestone, much has been said about the speed of the country's social and economic development. There is indeed a lot to be thankful for: visionary politicians, careful policy planning and the hard work put in by the pioneer generation.

For me, all this looking back has thrown up wonderful memories of the past. Some of these, captured in the photographs, headlines and words of this newspaper, are on display as part of the Singapore STories: Then, Now, Tomorrow exhibition at the ArtScience Museum until October.

Other memories have been triggered by pictures people have posted on Facebook, Instagram and on portals such as the Singapore Memory Project of places, food items, toys and stationery that used to be part of our everyday lives in the 1970s, 1980s and 1990s.

For me, however, the best memories are the ones that come suddenly and quite unannounced as you are walking in a mall or driving past a familiar street corner.

And while there is something to be said for the shared collective memory of Singaporeans who remember Green Spot soft drinks and Kaka crackers, or playing Octopus and Parachute on Game & Watch devices, the deepest memories of Singapore are often the ones that are most personal and tell you something about your life and the people you love.

Like the clinic that my late grandmother used to take me to every Saturday morning in Parklane Shopping Centre, which in the late 1970s was one of the newer malls in town. She saw the doctor there nearly every week to monitor her hypertension and I would play and wander through the corridors of the place as she waited.

Later, my dad would pick us up in his car after what was then a compulsory half-day of work.

Sometimes we would go to Parklane in mid-week after school just to pick up her medicine, after which we would take a trishaw to Chinatown. There, she would often stock up on talcum powder that came in a block shaped like the DBS logo. I used to marvel at the old-new shiny patina of the bronzed box.

Recently, I went back to the mall in search of a new vinyl record store that had opened and was amazed to find there is still a clinic in the exact same spot on the third floor - a minor miracle, really, in today's constantly changing retail landscape.

Another place that sends chills down my spine is the corner of Queen Street and Stamford Road, where a big bus stop that served the old National Library used to be.

This was where my Catholic High School classmates and I used to gather immediately after school, together with other kids from St Joseph's Institution and St Anthony's Convent, excitedly discussing the afternoon ahead. Should we go home or catch a movie and wander the malls in Orchard Road? Often, the decision was made simply by which bus pulled up next at the giant bus bay.

But there were also moments when the group was smaller and we got lost in discussions with our best friends about our lives.

The buses would come too soon before we could finish, so we sat at the "S11" open-air food court behind the bus stop, just talking, drinking bandung and letting the buses go by.

Sometimes, I would take a friend's bus because I didn't want the conversation to end, only to have to rack my brains later on where I should get off and get another bus to find my long way home.

Today, of course, the bus stop, the coffee shop and the library are all gone. But the intersection is there and in the place where the bus stop used to be, the Singapore Management University is building an extension for its law students - a gathering of young people of a different sort.

American singer-songwriter Suzanne Vega put it most poetically in a song she wrote a few years ago about meeting a childhood friend.

"Zephyr and I sort out our long time memories

Do you remember, he says, the 1970s

This was a youth mall of America on this street

All of us hanging here like underage cops on a beat

And the wind kicks up in the smell of rain

Now the kids are gone but their souls remain

The graffiti goes but the walls retain

The flowers go but the earth must still remain."

From the days when cameraphones and the Internet did not exist, these small markers in Singapore's built heritage - the street corners and bus stops, the little details in restored buildings - hold the key to unlocking some of the sweetest recollections that Singaporeans have.

So happy 50th birthday Singapore and thanks for all the memories.

My birthday wish for the nation is that in the rush to make more of them, let's not lose the ones we still have.