Millions of New Yorkers and visitors ride the city's subway and other trains each day. The public transportation system offers more than just a trip, however. It also has one of the most extensive public art collections in the world, with much of it under city streets.

Some people call it New York's "underground art museum." It includes more than 250 works of art. They are meant to brighten everyone's ride around the city.

There is the huge painting of the night sky on the ceiling of Grand Central Terminal. New Yorkers have been looking up at that artwork for 100 years.

In the nearby Grand Central Market, you can find a large, crystal light fixture. The ice-like stones hang on the chandelier's many branches, making the piece look like an upside-down olive tree. Sculptor Donald Lipski completed the work in 1988.

Other artists include new ones and the long-famous: Roy Lichtenstein's pop art porcelain enamel mural is found at Times Square. Sol Lewitt's intensely colored "Whirls and Twirls" is at Columbus Circle.

Sandra Bloodworth has directed the Metropolitan Transportation Authority's arts program since it began in 1985.

"But actually, it really began much earlier. When the subway was founded in 1904, a percentage, if you will, of money was set aside to create a special ornamentation within the system, in order to make the place this very special place that people would want to use."

For the past 30 years, artists have been asked to make works that relate to city life or to the neighborhood around a train station. There are coastal scenes at stations near the Atlantic Ocean. Native plants and flowers can be found in a garden scene in Brooklyn.

Wildlife mosaics greet visitors arriving at the subway station next to the American Museum of Natural History. Sculptor Tom Otterness created the small, rounded, metal creatures that populate another station.

At Times Square, Jane Dickson's mosaics of "The Revelers," suggest New Year's Eve celebrants. Rider Tonya Pierre praises the underground art.

"When I'm stressed, I look at the subway art. I love the colors. Where I live, they have a mosaic of a man and a woman, like, floating across the water, and it's beautiful. It's just beautiful to have art everywhere."

Nearby is Alejandra Acosta, a visitor from Colombia. She stopped to take a picture of a colorful glass mosaic mural by the former artist Jacob Lawrence.

"I think it's nice when you see these kinds of things that catch your eye when you're walking in spaces like the subway stations that seem a little bit dull. They don't have a lot of decoration."

The new Fulton Center train station connects nine major subway lines. A massive work by James Carpenter sits atop the center. Sandra Bloodworth calls it the Metropolitan Transportation Authority's "crowning piece of art."

"Together they've created this work of art that brings light into the station. As Jamie Carpenter says, the sky is folded onto the sky reflector and down onto the people as they travel through the station."

Even on cloudy winter days, the piece brings life into the dark passages. The same could be said, in fact, about all the works in New York's underground art museum.

I'm Caty Weaver.