The interior of the St Sampson`s Cathedral is composed of three spaces – the so-called refectory, which houses the chapels devoted to John the Theologician and Michael the Archangel and the main body of the church with a high altar at the end.
St Sampson`s Cathedral is a rare St Petersburg’s church that has preserved most of the images dating from the 1720s-60s, including the signed icons by A. Kvashnin, A. Pospelov and T. Bazhenov. Among the church icons are specimens dating from the late 17th to early 20th centuries.
Noted for its rich and varied ornaments, the high altar in the Empress Ann style was executed of pinewood and its carvings and sculpture – of lime. Its composition synthesized ancient Russian traditional canons and European influences. The iconostasis takes up the eastern wall and includes 48 icons. It is 13,6 m wide and 11,2 m high at the central point. It consists of five tiers (or in Slavonic usage, ranks), and includes: the local, festal, diesis, the prophets’ and the forefathers’ tiers.
Along with icons, the conception of the iconostasis is realized through its sculpted decoration, for example, by sculptures in the forefathers’ tier, and also by those of The Most Holy Mother of God and St Apostle John the Theologician, flanking the icon Crucifixion.
The north and south chapels house smaller, four-tier iconostases with 18 and 22 icons, respectively. The decor reflects the transition period of their execution. Baroque cartouches and rococo volutes intervene with classical elements – rosaces, festoons and fluted pilasters.
On the north and south walls of the refectory are the largest Illuminated church calendars in St Petersburg, dating from the late 17th century.
At various points in time narrative paintings were created on the church walls and vaults, the finest of those is the painting in the main nave that depicts victorious Peter I at the battle of Poltava. In the 1900s a painting Sampsonievsky Temple was created that is attributed to the painter I. Petrov. On the western refectory wall are two pair compositions The Symbol of Faith, on the eastern altar walls of smaller iconostases is God Savaof. During the 1908-09 restoration, on the arched vault of the eastern refectory wall there appeared a painting showing two angels crowning the Kazan Icon of the Mother of God with a crown of Glory. According to legend, this image favored the Peter’s army at the Poltava battle.
In the central nave there is a chandelier of silver-plated copper and bronze made by Russian craftsmen. The six-tiered chandelier is crowned with a ball and a cross.