For more than 25 years the MTA Arts for Transit program has been responsible for transforming our underground into a vast canvas for public art. Mosaics, glass, bronze and other materials now adorn the previously decaying and forgotten walls and corridors of our subways. In honor of Arts for Transit passing this quarter-century milestone, SundayArts took a look at some of the system’s most celebrated works and the artists behind them. This week we focus on Tom Otterness’s, “Life Underground.”