Tucked away in the heart of London's Square Mile, a 150m-year-old ammonite stares out at passersby from between windows of a tapas restaurant. The fossil is nestled in a limestone wall on Plantation Lane alongside remnants of ancient nautiloids and squid-like belemnites - a hidden mineralised aquarium that offers a glimpse into deep time.
Joining Dr Ruth Siddall, a geologist with a passion for urban geology, on one of her walking tours reveals the often-overlooked world of stones that make up our cities. The architecture of central London is, in fact, a largely unwitting showcase of Earth science through the ages. "London is huge," Ruth explains, "but unlike some cities it has no local building stones of its own. It's basically in a basin of clay, so all the stones you see around us have had to come from elsewhere."
The tour begins with York stone - a fine-grained sandstone that was once a prehistoric riverbed, 310m years old and quarried in the Peak District. Alongside it, serpentinite from the Italian Alps and larvikite from Norway are just a few of the many stones on display. At each stop, Ruth points out the unique features and stories behind the stone, revealing the epic journey they took to reach their current location.
A visit to St Paul's Cathedral reveals fossilised orthocones embedded in the limestone exterior of a wine bar - a 150m-year-old vertebrate bone that might be from a pterosaur. Meanwhile, the co-working space on Houndsditch boasts an exterior constructed of gneiss from a meteorite impact crater in South Africa. The stone's surface still bears the patterned veins of black impact glass, carrying traces of extraterrestrial minerals and having originated 6,000 miles away.
This walking tour offers a unique perspective on the city - one that transcends its usual grandeur to reveal the fascinating stories hidden within the stones themselves. And it's an experience that will leave even the most seasoned geology enthusiast in awe.
Joining Dr Ruth Siddall, a geologist with a passion for urban geology, on one of her walking tours reveals the often-overlooked world of stones that make up our cities. The architecture of central London is, in fact, a largely unwitting showcase of Earth science through the ages. "London is huge," Ruth explains, "but unlike some cities it has no local building stones of its own. It's basically in a basin of clay, so all the stones you see around us have had to come from elsewhere."
The tour begins with York stone - a fine-grained sandstone that was once a prehistoric riverbed, 310m years old and quarried in the Peak District. Alongside it, serpentinite from the Italian Alps and larvikite from Norway are just a few of the many stones on display. At each stop, Ruth points out the unique features and stories behind the stone, revealing the epic journey they took to reach their current location.
A visit to St Paul's Cathedral reveals fossilised orthocones embedded in the limestone exterior of a wine bar - a 150m-year-old vertebrate bone that might be from a pterosaur. Meanwhile, the co-working space on Houndsditch boasts an exterior constructed of gneiss from a meteorite impact crater in South Africa. The stone's surface still bears the patterned veins of black impact glass, carrying traces of extraterrestrial minerals and having originated 6,000 miles away.
This walking tour offers a unique perspective on the city - one that transcends its usual grandeur to reveal the fascinating stories hidden within the stones themselves. And it's an experience that will leave even the most seasoned geology enthusiast in awe.
. The fact that the architecture is made from stones that came from elsewhere because of the city being in a basin of clay makes total sense. It's like, no wonder we don't have our own local building stones! 
. And the co-working space with gneiss from South Africa? That's just crazy cool 
. I need to check out this walking tour ASAP!
! The fact that gneiss is from a meteorite impact crater in South Africa and has black impact glass veins is just mind blown 
And can you even imagine the history behind those 150m-year-old pterosaur bones 
embedded in St Paul's Cathedral? Like what was it doing flying around over London back then? 
I'm totally taking this walking tour now 
. The walking tour itself sounds like an amazing experience, but I'd love to see more of it being made available online too - maybe some kind of virtual tour or Google Earth layers so we can all explore together 
.
it was like a treasure hunt but instead of treasure its just REALLY OLD ROCKS 
anyway i'm totally convinced now that london is basically one big geology lesson in disguise 
OMG I just found out about this super cool walking tour in London where they take you to all these ancient fossils and rocks just chillin between buildings 
I mean, I get what they're trying to do here, but can't we just have a decent Google Maps view of the city instead? 
I mean, I love a good snack as much as the next person, but come on, can't we have a proper museum exhibit or something instead of this "hidden mineralized aquarium" nonsense? 
The only cool thing about this tour is that it's not totally boring to walk around central London, but other than that... 
just found out that those beautiful old buildings in London are literally just sitting on top of ancient fossils and rocks from other parts of the world - no native limestone to speak of... 310m year old York stone is just a reminder that everything is borrowed and nothing's truly original 
And can you believe some of those stones have traveled over 6,000 miles from other parts of the world? Mind blown, right? 
And can you believe the stories these stones have to tell? From prehistoric riverbeds to meteorite impact craters... it's like having a piece of Earth's history on our doorstep! 
I'd totally book that walking tour in a heartbeat - who knew geology could be so cool?! 
The idea of these stones having traveled 6,000 miles from South Africa to end up as a meteorite impact crater in London is mind-blowing, right?! 
. This tour is giving me all sorts of feels - I'm hooked! 
, and these experts are showing us how our city is literally built on stones that have been on earth since dinosaurs roamed free