Saint Isaac's Cathedral is the largest Russian Orthodox cathedral in St. Petersburg. Dedicated to Saint Isaac of Dalmatia, its impressive 101.5 meter high dome (the fourth largest by volume in the world) is plated with pure gold. The bronze doors of the cathedral are modelled after those made by Lorenzo Ghiberti at Saint Giovanni's Baptistery in Florence. These detailed reliefs, however, are designed by Ivan Vitali. Inside, don't forget to look up and spot the small white dove suspended from the top of the cupola meant to represent the Holy Spirit. This stunning building inside and out is worth a visit on any trip to St. Petersburg!