Besides zipping travelers across the island, the Montreal Metro doubles as the city’s most expansive art gallery. Each of its 68 subway stations is a distinctly designed synthesis of architecture and art, and many prominently feature sculptures, mosaics, and stained glass. Even for longtime residents, visiting a new stop for the first time can feel like an adventure. Two of the most photogenic artworks in the metro are no doubt the stunning stained glass windows at Charlevoix station. On sunny days, they cast kaleidoscopic hues across crowds going up and…