FLINT, MI -- When Scot Thompson was about 20, he decided it was time to grow up and stop playing with Legos.

He held out for about 10 years, still going into Lego stores and looking, while refraining from buying anything. Then, one day his family bought him a small Lego train from a garage sale and he just couldn't take it anymore.

Now the 39-year-old registered nurse and president of the MichLUGS Lego group spends anywhere from 24-48 hours a week building with Legos. The fruits of all that labor are now on display at the Flint Institute of Arts.

The display -- six buildings that are all replicas of actual buildings in Saginaw -- are among other works on display in the FIA's art school between March 1 and April 5. On March 28, there will be an open Lego-building competition.

It's a chance to see how what started as a child's building toy can become art and a reminder that our creativity, even if expressed through such toys, is something to be embraced.

For Thompson, once he had that train, he started to build.

"I was like, I have mass transit. Now I have to build a city," he said.

He made 52 small, crude, buildings. But it was just the beginning. He couldn't stop.

The most impressive is the model of the Castle Museum in Saginaw, full of spires and towers that make it live up to its name.

There's also the Temple Theatre, the Hoyt Library, First Merit Bank, the Ippel Building (not a large building, but one with sentimental value as they were the first to display Thompson's work), and the Potter Street Station, a long-vacant train depot.

It's about half of his Saginaw collection. He also has buildings from Bay City where he lives, and Detroit, Pontiac, Fenton, and Germany.

The first building he took seriously once he regained his love for Legos was the Bay City Hall. It has a clock tower. Thompson loves clock towers.

What sets the work of Thompson and those like him apart -- not to mention those who compete at the FIA in March -- is that unlike the Lego sets you buy with directions, Thompson "free-builds."

Everything he makes is from scratch. He goes to Lego stores all over the country buying different-colored bricks and plates and other parts, thinking about how he can reuse or repurpose them.

Take, for example, the clock tower on the Potter Street Station. The clock hands, if you look closely, are actually hands -- more specifically, arms. The hour hand is the arm of a robot and the minute hand is the arm of a Star Wars battle droid.

Or the streetlights that line the city he's built. They look real enough that you might think they come prepackaged as streetlights, but they're his own design and took some special engineering. A plastic Lego pin runs through the post, keeping it all together as he had to put in some pieces upside down to get the look he wanted. And the lamps themselves, the transparent yellow lights at the top, are actually from Star Wars blaster guns.

Depending on the building, it can vary in how long it takes him to build one. The one-story Ippel Building took a day of planning and building. He sat on the Castle Museum for a year, slowly accumulating parts and figuring out how he would build it.

It also depends on time and how "in the zone" he is. It took him 27 hours to build the First Merit Bank building -- 27 straight hours.

"I loved it. I was so in the zone and didn't go to bed," he said.

What started as a passion for building also blossomed into a passion for history and architecture.

"Because it's so beautiful, you want to learn more about it," he said. "It starts out as, oh, it's pretty, I want to build it. Then you go a little deeper."

Now on the verge of turning 40, Thompson thought back on that unexpected gift of a train that started the hobby that takes up more of his life than his job as a nurse.

"They had no idea this would spark such an immense hobby," he said.