What's a 40-year-old architect from Newport Beach, Calif., doing with 45 tons of sand dumped inside the South Towne Mall? Why, building a giant sand castle of course.

"I'm 40 going on 13," laughed sand sculptor Kent Trollen. "I had a guy who came up to me yesterday and said, `Aren't you a little old to be doing this?' I asked him if he wanted to join me and he just smiled."Trollen's company, Sandcastles Unlimited, was hired by the mall to create a sculpture for its "Beach Party" promotion. Although the promotion ended Saturday, the castle will remain on display through April.

Work on the project began a week ago, when the sand was packed into forms similar to those used to mold concrete. Once it had been compacted to make the structure sturdier, Trollen and his assistant started to sculpt.

They had no idea how the finished castle would look when they shaped the tips of the top turrets. That's the way Trollen likes to work, relying on inspiration that "just falls out of my head."

The fact that his work eventually will be reduced once again to a pile of sand doesn't bother Trollen, who has been doing this professionally for eight years.

"If you could freeze it and make it stay around forever, it wouldn't be a sand castle," he said. "It's like life. It's not going to be around forever so you have to enjoy it while it's here."

Although he earns his living as a designer of buildings that people can inhabit, Trollen said he most enjoys creating structures that can be dwelt in only in the imagination.

"It's magic," he said of the reaction to his work, which he said appeals more to adults than to children. "There is a special place in everyone's heart for it."

Including his own. Trollen said that when he finishes a piece, he likes to meditate beside it for a while. "I sit and look at it quietly, maybe take a few pictures and then go home."