10 Fascinating Facts About St. Paul's Cathedral You Didn't Know in London

When you walk through the heart of London, past the bustle of Bank and the clatter of the Tube at St. Paul’s station, you’re standing in the shadow of one of the most iconic structures in the city - St. Paul’s Cathedral. Most Londoners pass it on their way to work, tourists snap selfies from the Millennium Bridge, and visitors often mistake it for just another grand church. But this building holds secrets that even many who live in London don’t know. It’s not just a place of worship. It’s a survivor, a silent witness, and a masterpiece of engineering that still hums with stories from centuries past.

It Was Built After the Great Fire - and Almost Didn’t Make It

Before St. Paul’s stood where it does, there was an older cathedral that burned to the ground in the Great Fire of London in 1666. The fire didn’t just destroy buildings - it wiped out 13,000 homes and 87 churches. When King Charles II asked Christopher Wren to design a replacement, he didn’t just want a church. He wanted a symbol that London would rise again. Wren’s first design was rejected by the Church of England for being too bold. His second? Too radical. It took him over 30 years to get it right. The final version, with its towering dome, was inspired by St. Peter’s in Rome but adapted for London’s skyline and seismic conditions. The dome alone weighs 65,000 tons - heavier than the entire Eiffel Tower.

The Whispering Gallery Is a Natural Sound Lab

Inside the inner dome, just 257 steps up, there’s a circular walkway called the Whispering Gallery. If you stand with your ear against the wall and whisper, your voice travels clearly along the curved surface - even to someone 35 meters away. It’s not magic. It’s acoustics. Sound waves cling to the curve of the stone, bouncing silently from one side to the other. Locals bring their kids here on school trips, and couples often test it on dates. Tourists sometimes shout random phrases - “I love fish and chips!” - and are shocked when the words come back clear as a bell. The gallery was designed this way on purpose. Wren knew that sound would carry better in a space built for prayer, and he used geometry to make silence speak louder than noise.

It Survived the Blitz - Barely

During World War II, London was bombed nearly every night. St. Paul’s was a prime target. On December 29, 1940, incendiary bombs rained down on the City. Flames licked the roof. The lead on the dome melted. Firefighters worked through the night, using sandbags and hoses to douse the blaze. One photo from that night - now famous - shows the cathedral standing alone in a sea of smoke and fire. The image was used as propaganda: a symbol that London wouldn’t break. The cathedral’s roof was saved by a team of volunteers, many of them local men from nearby boroughs like Southwark and Islington. They didn’t have modern gear. Just buckets, ropes, and grit. Today, you can still see the charred marks on the wooden beams inside the crypt - a quiet reminder of how close it came to being lost.

There’s a Secret Room Beneath the Golden Cross

At the very top of the cathedral, the golden ball and cross that crown the dome aren’t just decorative. Inside the cross, there’s a small, sealed chamber. It was built in 1927 and contains items left by the architects and clergy: a copy of the 1927 Book of Common Prayer, a list of the cathedral’s staff at the time, and a newspaper from the day the cross was installed. It’s never been opened. No one knows when - or if - it will be. Even the Dean of St. Paul’s doesn’t have the key. It’s a time capsule meant for the future, and it’s been sitting there for nearly 100 years, untouched. Locals joke that when the next major event happens in London - say, a royal coronation or a second Brexit - someone might finally crack it open.

The Dome Has a Hidden Inner Structure

From the outside, St. Paul’s dome looks like one smooth curve. But it’s actually three domes stacked like Russian dolls. The outer dome is what you see from afar. The middle dome is structural - made of brick and timber, it holds everything up. And the inner dome, the one you see when you look up from the floor, is decorative. It’s painted with a fresco by James Thornhill, showing scenes from the life of St. Paul. The real genius? The middle dome is invisible from both inside and outside. Wren solved the problem of weight and visibility in one move. Most cathedrals have a single dome. St. Paul’s has a hidden skeleton. That’s why it didn’t collapse under its own weight - and why it still stands today.

It’s the Final Resting Place of National Heroes

Underneath the cathedral, in the crypt, lie some of Britain’s most revered figures. Admiral Nelson, whose victory at Trafalgar saved the country from Napoleon, is buried here. His tomb is carved from black marble and topped with a life-sized statue. The Duke of Wellington, who defeated Napoleon at Waterloo, rests beside him. Even the architect himself, Christopher Wren, is buried here - his tombstone reads, “Lector, si monumentum requiris, circumspice” - “Reader, if you seek his monument, look around.” It’s one of the most quoted Latin inscriptions in the UK. You won’t find plaques for pop stars or footballers. Only those who shaped the nation’s destiny are honored here. It’s a quiet hall of remembrance, far from the crowds above.

The Cathedral Has Its Own Post Office

Yes, you read that right. St. Paul’s has had its own post office since 1880. It was created so that letters sent from the cathedral - especially those from clergy or dignitaries - could be stamped with a special postmark: “St. Paul’s Cathedral.” Even today, if you write a letter and ask for the cathedral’s postmark, they’ll stamp it with a hand-stamped design of the dome. It’s a popular keepsake for tourists and collectors. Locals who live in the City of London sometimes send birthday cards from there as a quirky tradition. The post office is tiny - no bigger than a phone booth - and tucked away near the south transept. You won’t find it unless you ask.

It Was Once Used as a Military Headquarters

During both World Wars, the cathedral’s crypt was turned into a bomb shelter and command center. In 1941, British intelligence used the crypt to store encrypted messages and coordinate air raid responses. The stone walls blocked radio interference, making it the perfect place to send secure signals. Soldiers slept on straw mats in the chapels. The organ pipes were covered with sandbags to protect them from shrapnel. Today, you can still see the bullet holes in the stone arches near the west door - covered with plaques but never repaired. They’re left as evidence of what the building endured.

The Clocks Are Still Hand-Wound

St. Paul’s has six clocks - four on the exterior, two inside. None of them are electric. Every week, a team of volunteers climbs the narrow staircases to wind each one by hand. It takes about three hours. The largest clock, on the west face, is over 150 years old. Its pendulum swings once every two seconds. The bell that chimes the hour - called “Great Paul” - weighs 16.5 tons and is the heaviest bell in the UK. It was cast in 1881 and only rings on special occasions: royal birthdays, Armistice Day, or when the Queen Mother passed away. Most Londoners have never heard it. But if you’re in the City on November 11 at 11 a.m., you’ll know.

The View from the Top Is Better Than the Tower Bridge

Most tourists climb the Tower Bridge or the Shard for panoramic views of London. But the best view? It’s from the Stone Gallery, just below the golden cross. From here, you can see the entire City - the Gherkin, the Walkie Talkie, the Shard, and even the green of Richmond Park in the distance. You can spot the exact spot where the Great Fire started on Pudding Lane. You can see the Thames winding past the Tate Modern and the London Eye. On a clear day, you might even catch the lights of Windsor Castle on the horizon. Locals know this spot. They come here at sunset with a coffee from Pret or a sandwich from Marks & Spencer’s, and sit quietly as the city turns gold. It’s free if you’ve already paid to enter the cathedral. And it’s the only place in London where you can see the skyline without being surrounded by crowds.