Saint Isaac's Cathedral
It is the largest orthodox basilica and the fourth largest (by the volume under the cupola) cathedral in the world. It is dedicated to Saint Isaac of Dalmatia, a patron saint of Peter the Great, who had been born on the feast day of that saint. The cathedral took 40 years to construct, under Montferrand's direction, from 1818 to 1858. To secure the construction, the cathedral's foundation was strengthened by driving 25,000 piles into the fenland of Saint Petersburg. Innovative methods were created to erect the giant columns of the portico.The cathedral's bronze doors, covered in reliefs by Ivan Vitali, are patterned after the celebrated doors of the Battistero di San Giovanni in Florence, designed by Lorenzo Ghiberti. Suspended underneath the peak of the dome is a sculpted white dove representing the Holy Spirit. Internal features such as columns, pilasters, floor, and statue of Montferrand are composed of multicolored granites and marbles gathered from all parts of Russia. The interior was originally decorated with scores of paintings by Karl Bryullov and other great Russian masters. When these paintings began to deteriorate due to the cold, damp conditions inside the cathedral, Montferrand ordered them to be painstakingly reproduced as mosaics, a technique introduced in Russia by Mikhail Lomonosov.