→ The Jordan Staircase — The grand staircase was designed by Rastrelli and survived the 1837 fire. Named for the annual ceremony where the tsar descended to bless the Neva waters on Epiphany, the staircase is a masterwork of Baroque illusion — the mirrored walls and painted ceiling make the space feel twice its actual size.

→ The Malachite Room — After the 1837 fire, the Malachite Room was created using two tons of Ural malachite in the 'Russian mosaic' technique — thin slabs of the semi-precious stone were applied over a marble base with such precision that the seams are invisible. It served as the last waiting room of the Provisional Government before their arrest in 1917.

→ The 1941 Cellars — During the Siege of Leningrad, the palace cellars served as a bomb shelter and dispensary. The museum staff had evacuated 1.2 million artworks east by train before the blockade closed. The empty frames still hang in some galleries as a memorial to what was removed.

→ The Noon Cannon — Every day at exactly 12:00, a cannon fires from the Naryshkin Bastion — a tradition dating to Peter the Great. In the 18th century the shot marked the start and end of the workday and warned of floods; since 1872 it has marked noon. During the 1917 Revolution, this same cannon gave the signal for the cruiser Aurora to begin its advance.

→ The Trubetskoy Prison — Built in 1870–72 inside the fortress walls, this prison held political prisoners in solitary confinement. Dostoevsky was held here before his mock execution in 1849. The cells have original furniture and graffiti carved by inmates — including a calendar scratched into the wall by a prisoner counting his days.

→ The Imperial Necropolis — The cathedral floor is a pavement of tombstones covering nearly all Romanov rulers from Peter the Great to Nicholas II (whose remains were interred here in 1998). The simplest marker belongs to Peter himself — a plain marble slab, deliberately modest compared to the ornate monuments around it.

→ The Preserved Cobblestones — Beneath a canopy of jasper, rhodinite, and lapis lazuli lies the exact spot where Alexander II fell — the original cobblestones, iron railings, and pavement of the canal embankment have been preserved under glass exactly as they were on March 1, 1881.

→ The Coats of Arms — The bell tower is covered in 134 mosaic coats of arms representing the Russian provinces and cities that donated funds for the church's construction. Each province paid for its own panel, making the tower a political map of the empire in miniature.

→ The Concrete Foundation — Built on the edge of a canal, the church rests on a concrete foundation — a pioneering technique in the 1880s. A layer of clay was used to seal the foundation against water penetration, allowing the building to extend into the canal itself.

→ The 25,000 Piles — Because St. Petersburg is built on marshland, the foundation rests on 25,000 pine piles driven deep into the soft soil — a technique borrowed from Venice. The cathedral weighs over 315,000 tons and has settled unevenly ever since, causing the columns to tilt and cracks to appear in the marble walls.

→ The Malachite and Lazurite Columns — The iconostasis is framed by eight columns: six of Ural malachite and two of lapis lazuli, each 9.7 metres tall. Together they represent the finest surviving examples of 'Russian mosaic' — thin stone veneers applied over marble cores with almost invisible seams.

→ The Foucault Pendulum — In 1931, the Soviet government hung a Foucault pendulum from the dome to demonstrate Copernican theory — the 98-metre cable made it one of the longest such pendulums ever installed. The pendulum was removed in the 1990s but the mounting ring remains visible in the ceiling.

→ The Chess Mountain Cascade — East of the Grand Palace, the Chess Mountain cascade is a broad chute tiled in black-and-white marble like a chessboard, with water cascading down a stairway flanked by polychrome griffin sculptures.

→ The Trick Fountains — Peter the Great installed hidden 'trick fountains' in the Monplaisir Palace gardens — benches that spray unsuspecting sitters, paths that drench walkers from below, and hidden jets activated by guards. Designed to amuse guests at court, they still function today and catch visitors by surprise.

→ The Golden Enfilade — Rastrelli created a suite of state rooms called the 'Golden Enfilade' stretching the entire length of the building — the carved and gilded doorways create an unbroken vista of 60 metres through five antechambers, each more ornate than the last.

→ The Cameron Gallery — Catherine the Great commissioned Scottish architect Charles Cameron to add a neoclassical gallery to the south end. The 177-metre-long colonnade is a stark contrast to Rastrelli's Baroque — the empress considered the older style outdated and wanted the 'pure' lines of ancient Greek and Roman architecture.

→ The Missing Domes — Pre-war photographs show five gilded domes over the palace church. During the 1944 fire, the original wooden dome structures burned entirely. The current domes are a 1957 restoration — the original gilding was done with gold leaf dissolved in mercury, a technique so toxic it could not be replicated safely, so the new domes were gilded using an electro-chemical method.