Saint Isaac Cathedral, 2 hours

The Saint Isaac Cathedral is a great example of late Classicism. It took 40 years to build it, 60 of the 440,000 construction workers died just of inhaling the mercury fumes while decora-ting the cathedral's dome with 100 kg. of pure gold. St. Isaac’s Cathedral is 101.5 m tall, it has 112 monolith columns about 114 tons each, 14,000 people can attend services held here on big religious holidays.