Its history is nearly as long as that of St. Petersburg. The original Church of St. Isaac was first ordered by Peter the Great in 1706. The little wooden building, dedicated to the Tsar's patron saint Isaac of Dalmatia hosted his wedding ceremony with Catherine I 6 years later. This wooden church stood for another five years until Peter ordered it to be replaced by a new “Petrine Baroque” stone structure that was completed after the Tsar’s death in 1727.
After suffering significant damage from a poorly constructed foundation and marshy subgrade, the church was replaced by Catherine II the Great, who hired Antonio Rinaldi to construct a new late Italian Baroque cathedral. She liked the design so much that she ordered 5 such churches to be built. The only one still standing today is in Kingisepp, east of the city. The Rinaldi church on St. Isaac’s square was finished with brick by Catherine’s son Paul and consecrated only in 1802, long after Catherine’s death.
It stood for only 7 years before Tsar Alexander I, Catherine’s grandson, held the first competitive bid to replace the structure with a grand cathedral. It took many years before he found a suitable designer, French architect Auguste Montferrand who opted for a full dome constructed of cast iron set upon a drum. It took 40 years to complete the building.
Take a look around Saint Petersburg and spot a glimpse of St Isaac's Cathedral:
The estimated cost Russia spent on the cathedral's construction is unfathomable. About 10000 logs were driven into the ground below it to improve the marshy ground, 882 pounds of gold, 16 tons of malachite and a thousand tons of bronze were used for the interior. The mosaics on the walls cover 7,108 square yards. The great dome's gold plating, that was applied using a process that involved spraying the metal onto its exterior surface, ultimately poisoned to death 60 or so craftsmen.
Yet the sheer size of the cathedral designed to hold 14000 standing guests leaves an unforgettable impression, especially when looking up at the artistic marvel of the great dome from the inside.