In Moscow, some of the best architecture may lie many meters underground. With its vaulted ceilings, marble floors and tiled mosaics of Vladimir Lenin and the Red Army, the Moscow metro is a crown jewel of the Russian capital. In the decades since Muscovites boarded the first train, 90 years ago this week, the metro system has grown to meet the demands of the ever-growing metropolis. Each day, millions of commuters in the city of 13 million crowd into the metro's 302 stations to ride on one of 1