The State Museum St Isaac's Cathedral is a museum complex consisting of the exquisite Smolny Cathedral, a masterpiece of Rastrelli’s baroque; the Church of the Savior on Blood which highlights shimmering mosaics and marble floor patterns; St Sampson`s Cathedral with its ancient icon-painting and carved iconostases and the grand St Isaac’s Cathedral which features icons of golden mosaics and columns of malachite and lapis lazuli. St Isaac’s Cathedral is an outstanding monument of Russian architecture of the 19th century and one of the greatest dome constructions in the world. These churches of ecclesiastic architecture differ from each other greatly, yet they all form part of the museum complex of St Isaac’s Cathedral also known as ‘The museum of four cathedrals”. The Museum takes great care in preserving and restoring these Russian heritage cathedrals, whilst all four continue to remain active Orthodox churches.