Lucina and I crossed the Millennium Bridge discussing a man who had broken her heart, and eating candied peanuts, which smelled far better than they tasted. From the opposite side of the bridge, a fragrant plume of cinnamon sugar with hints of warm nuttiness drew us over the steady Thames. At the river’s center, a hearty man with a stainless-steel cart churned a vat of glistening brown syrup and scooped crystalized peanuts into rows of clear plastic cups. For a pound, he offered us the fresh, piping hot batch. It was our final week as visiting students in London, and this chill, clear day was a feast.

As an English literature student, I was obligated to spend my days neck deep in medieval verse. Most days, however, “endless blisse” could not come soon enough, and I opted to walk the streets instead, often accompanied by a classmate like Lucina. That day with her, as we took the South Bank walk along the Thames, making our way through Trafalgar and eventually to Soho, London was more alive to me than ever. It was a week from Christmas, and the streets were bustling with shoppers and brightened with lights, banners, and carolers. The work of the semester was nearly over, and a nostalgia for my time there had begun to sink in.

The modernity of London dazzled me, from its seamless transport system to its bizarre skyscrapers and diverse neighborhoods. Conversely, for all the striking features of development around the city, there was always a stately local pub or moss-covered ruin just around the corner. Lakes were spotted with swans and broached with womanly stone fountains, and canal narrowboats skimmed through green water and willow drapery. So, even if I hadn’t been reading such ancient texts, the city of London felt, as it must surely to all visitors, pervasively and tangibly old.

Through it all ran the Thames—as many have noted, old and steady yet ever surging, changing, like London itself. Moving briskly, perhaps still discussing love, Lucina and I passed under the Southwark Bridge and noticed an engraved stone mural along the wall. It depicted the Thames, its waters unexpectedly a setting for snowflakes, men pulling boats on wheels, market stalls and ice-skaters. An inscription that danced along its length read:

Behold the Liquid Thames frozen o’re,

That lately Ships of mighty Burthen bore…

And lay it by that ages yet to come

May see what things upon the ice were done.

I had never seen snow pile up in London or even witnessed anybody wearing real winter boots. The only “winter wonderland” I had experienced in London was the alpine-themed amusement park that had sprung up for the season in Hyde Park. In fact, these friezes, by the artist Richard Kindersley, depict a tradition now lost to London: the Thames frost fairs.

Every twenty years or so from the 17th to the early 19th centuries, temperatures dropped low enough in London to cause the River Thames to completely freeze over. And with the Thames frozen thick enough to walk on, the miserable cold was transformed into a cause for spontaneous celebration.

Take, for example, the 1814 frost fair, the last of its kind. When the ice solidified that winter, people flocked to the riverbanks and slowly gained the confidence to venture out. A thoroughfare dubbed “City Road” was established and lined with colorfully decorated shops and booths. Trinkets were sold at three times the normal price. Ten printing presses were there to document the occasion. Books and toys were sold; there was dancing, skating and music, and plenty of beer, gin, gingerbread and roasted meat. There was even an elephant. After two days’ worth of revelry, the river began to thaw again, and the crowd thinned, escaping the danger of the cracking ice.

It was not all fun and games when the Thames froze. Its bustling ports became unusable, and trade stood still. In fact, people made up for lost profits by opening fair stalls. The ice did thousands of pounds in damages to houses, shops, boats and bridges. And worst of all, people sometimes fell through the ice and drowned. Many froze to death in the city and in even greater numbers in the countryside.

For a moment, though, the people of London took advantage of the opportunity afforded by a perilous phenomenon to create a public place infused with a rare magic. In her novel Orlando, Virginia Woolf describes the beauty of a Thames frost fair. In 1608, the king orders the frozen river to be prepared for his citizens with “arbours, mazes, alleys, drinking booths,” and conducts matters of state and war right there on the ice under “plumes of ostrich feathers.” In a beautiful passage, Woolf writes:

“Frozen roses fell in showers…. Coloured balloons hovered motionless in the air. Here and there burnt vast bonfires of cedar and oak wood, lavishly salted, so that the flames were of green, orange, and purple fire … there could be seen, congealed at a depth of several feet, here a porpoise, there a flounder…. But it was at night that the carnival was at its merriest … the nights were of perfect stillness; the moon and stars blazed with the hard fixity of diamonds, and to the fine music of flute and trumpet the courtiers danced.”

In this fantastical, timeless landscape, the protagonist Orlando meets the first true love of his life, a Russian princess he calls Sasha. His surmounting adoration of her, as he strives for the perfect poetry to describe her, mimics the elaborate and elegant construction of the fair. Likewise, the improbability of their union is mirrored by the fair’s surreal and rare occurrence, a scene of suspended time and reality. So that, when Sasha leaves Orlando, the ice that had been 20 feet thick for months suddenly fissures, sweeping floes, people and cats down the frigid river to their certain demise. Orlando stands on the bank, furious and heartbroken, watching it all surge away.

Though likely not as ornate or stately as Woolf’s, there were many fairs, each of which offered its own innovations and diversions. Some popular pastimes from the 1607–8 fair included throwing rocks at chickens, getting a shave from the barber, and bowling. Bull-baiting was recorded in 1688–9, a bloody sport in which dogs are set against a tethered bull. Bull-baiting turned to bear-baiting in 1788–9, a century later. That fair also saw a menagerie and puppet shows.

The goings-on at the outdoor Christmas markets I visited in London were not as riotous, but something of the spirit of the frost fairs seems to live on in them. So, what caused the Thames to freeze so thoroughly back then when today it barely so much as snows in London? What allowed for the frost fairs, and why haven’t they—like many of the city’s other relics—stuck around?

For one, the frost fairs occurred during a period of cold weather referred to as the Little Ice Age. In the period from the 15th to the mid-19th centuries, the average global temperature dropped by half a degree Celsius. Some places changed more than others, particularly the northern latitudes. The annual mean temperature in England was almost full degree C colder than it was in the following period of 1920–60. Elsewhere, glaciers expanded and overtook villages. In addition to the cold and ice, sickness and famines also claimed lives.

Scientists do not fully understand what caused the Little Ice Age. Data from tree and ice cores suggests that there was a drop in solar energy—incoming radiation from the sun. The sun’s activity, including the radiation it gives off and the number of sunspots, fluctuates periodically. It could have been volcanoes too. There is evidence that there were more volcano eruptions after 1200; the ash volcanoes spew into the air cools the earth by blocking out the sun.

So, it would seem that a natural trend towards warming after the 1900s accompanied by the warming effect of anthropogenic climate change is what makes frost fairs in 2018 impossible. But that’s not the whole story. The freezes in fact had as much to do with fluctuations in Earth’s climate as they did with architecture.

The London Bridge you see today—the location of the old frost fairs—is not the same bridge you would have seen as one of the fair’s attendees. You would have seen the original Old London Bridge, made up of almost 20 narrow arches and capped with homes, shops and a bustling street. The many narrow arches of the Old London Bridge—compared with the three wide arches of the current London Bridge—help explain why the Thames used to freeze over. The arches caused the water to flow at a much more glacial pace, and still water freezes easier than flowing water. Additionally, when less water made its way up from the sea, the lowered salt content raised the water’s freezing point. Sometimes ice floes would get stuck in the arches and block the river entirely.

Speaking in terms of vast geological time, the ways in which Earth’s climate has historically regulated itself and the ways in which it has so dramatically shifted can make the concept of anthropogenic climate change seem insignificant and pointless. Why bother thinking about climate change when another ice age could pop in any day now? Why bother thinking about climate change if we have no control over our broader planetary fate?

But the situation surrounding the Thames frost fairs offers a compelling reimagining of scale, particularly regarding how we contextualize human actions in relation to the cosmos. Those Londoners were trapped in a particularly cold era. They were, like all living things, at the mercy of the elements. And so, the fairs stand as a testament to the human capacity for joy, resilience and creativity in defiance of troubled times.

However, the freezing of the Thames was a largely human-made environmental condition. I like to imagine that if the people of London had known about the bridge’s role in the freezing of the Thames, they would have considering rebuilding. Because no matter how grand the fair was for those with the privilege to enjoy it, the city could have been altered in a way that saved the lives and livelihoods of those worst affected by the freeze.