Trinity Cathedral as you see it today dates from the 17C. The former building went up in smoke in 1649 when a stock of gunpowder kept in the basement exploded. The treasures inside are well worth the visit: remarkable murals by the great muralists Guri Nikitin and Sila Savin (1684) covering every inch of the sanctuary; the gilded five-layered (mid-18C) iconostasis and 16C copper holy doors escaped the explosion.