"Don't it always seem to go," sang Joni Mitchell, "that you don't know what you got till it's gone."

But Salt Lake City's Trolley Square, at age 100, is singing a different tune: "Don't it always seem to go, you're always glad when you save what you've got."

As homes, malls and neighborhoods have come and gone, Trolley Square has stood solid and stolid at the heart of town. That's one reason we need it — the more things that are secure and steady we have in life, the more secure and steady we feel.

But more than that, Trolley Square is important because it's a time capsule. Even in its new, refurbished state, just walking through the doors can open up the past.

In this centennial year, the history of the place is being revisited — how E.H. Harriman sunk $3.5 million into a new, mission-style car barn in the old LDS 10th Ward area of town; how the structure was saved from destruction in 1972 and granted historic status the following year; how it became the second most visited venue in Salt Lake City and was added to the National Historic Register in 1996.

But it's the "personal history" of the place that interests most — all the memories forged there over the years. Like the people of Salt Lake City, Trolley Square has been through a lot in a century. Most recently there were the shootings that many feared would keep shoppers away from the place for good. But the visitors returned. And now, a new refurbished look is slowly putting to rest the ghosts of the past and promising a vibrant future.

Over the years Trolley Square could have been turned into many things — from a parking lot to a condo village. But fortunately for Utahns, it has retained its look and character and its link with the past.

In every Utah town, citizens can name structures they wish were still around — that old post office in Brigham City, for example, or the old tabernacle in Coalville and those old rock houses in Farmington. The list is long. As with people, when an edifice makes it to 100 without getting wiped out, just the staying power alone is worth celebrating.

The lessons of Trolley Square are many, but one of the most important is this: Sometimes what is old is not simply outdated. Sometimes what is old can teach us about the past, anchor us in the present and give us firmer footing into the future.

And that is true not only for people but for "car barns" with a legacy, like Salt Lake City's Trolley Square.