STONE FORESTS OF THE SILURIAN: GOTLAND'S FOSSIL REEFS

Raukar: Gotland, Sweden's Limestone Sea Stacks 

Along the rugged Baltic shoreline of Sweden's enchanting island of Gotland, hundreds of towering limestone sea stacks known locally as raukar rise from the coast like ancient stone guardians.

If there is such a thing as a fossil hunter's happy place, Gotland is surely in the running. 

They rise from the beaches like ancient stone sentinels, sculpted into improbable shapes by wind, waves, and ice. 

Some resemble castles, others giants, and a few look suspiciously like they are waiting for someone to tell them a very old secret. The wonderful thing is... they already are.

Gotland, Sweden's Sea Stacks

These remarkable formations began life some 400 to 450 million years ago, during the Silurian, when Gotland lay not in the cool waters of the Baltic but close to the equator beneath a warm, shallow tropical sea. 

Instead of pine forests and seabirds, this was a dazzling underwater reef alive with corals, stromatoporoid sponges, algae, brachiopods, trilobites, crinoids, nautiloids, and countless other marine creatures.

The reefs themselves were built by tabulate and rugose corals—ancient relatives of the stony corals that still build reefs today. 

Their ancestry stretches back over half a billion years, though these Silurian reef-builders belong to groups that disappeared long ago. The familiar corals of our modern oceans are evolutionary cousins rather than direct descendants, continuing the remarkable story of reef-building through entirely different lineages.

Among the corals grew stromatoporoids, reef-building sponges that were every bit as important as the corals themselves. Layer upon layer, generation after generation, these organisms constructed vast limestone reefs teeming with life.

Then the world changed.

Continents drifted. Seas retreated. Mountains rose elsewhere. Gotland slowly travelled north with the moving tectonic plates until these tropical reefs found themselves in what would eventually become the Baltic Sea.

The Ice Ages did the rest.

Glaciers ground across the landscape before melting away, and over thousands of years waves relentlessly attacked the limestone coastline. Softer rock disappeared first while the toughest parts of the ancient reefs resisted erosion. What remains today are the raukar—the fossil-rich cores of reefs that once flourished beneath tropical sunshine hundreds of millions of years before the first dinosaur ever took a step.

Some of the finest places to explore them include Langhammars Nature Reserve on nearby Fårö, where magnificent raukar rise from broad pebble beaches that are wonderful for spotting weathered corals and crinoid fragments. 

Just up the coast lies Digerhuvud Nature Reserve, Sweden's largest concentration of sea stacks, where hundreds of limestone towers stand shoulder to shoulder beside deep blue water. On Gotland itself, Lergrav offers striking gate-like limestone formations surrounded by richly fossiliferous shoreline.

The beaches reward patient eyes. It isn't unusual to find honeycomb-patterned tabulate corals, horn corals, crinoid stem segments that resemble tiny stone beads, brachiopod shells, bryozoans, stromatoporoid fragments, and the occasional trilobite or cephalopod preserved in the limestone. Every pebble has the potential to hold a glimpse into a vanished tropical ecosystem.

One of the pleasures of visiting Gotland is that you may collect loose fossils found naturally on the beaches as keepsakes of your adventure. What you may not do—and quite rightly—is hammer or chisel fossils from the raukar themselves. These extraordinary formations are protected natural monuments that have survived nearly half a billion years. They deserve to greet generations of future fossil hunters just as they greet us today.

Late spring through early autumn, from May to September, offers the finest weather for wandering these spectacular coastlines. I prefer the rainy days as they wash away the tourists and only the hardy venture along the foreshore. The Baltic sparkles, wildflowers dot the limestone meadows, and every tide seems to reveal another fragment of an ancient reef. Picture all that with some sea mist and you've ventured into my happy place. 

Standing among the raukar, it is wonderfully easy to forget what century you're in. When we think of ancient Sweden, for some of us it is the image of the Vikings that come to mind. For others, our imaginations venture farther back to the origins of these stone towers and their dramatic stories. 

It is a delight to get to visit these last surviving skeletons of one of Earth's great tropical reef systems—a place where ancient corals quietly built cities beneath warm Silurian seas, leaving behind a story written not in books, but in limestone.

Här känns varje steg som en promenad genom havets allra äldsta minnen. (Here, every step feels like a stroll through the sea's oldest memories.)

If you're planning to visit Sweden and their marvelous sea stacks and need a wee bit of enticement to encourage your friends and family to join you, I have put together a list of extra goodies for all tastes.

Sweden has so much to offer, but three of its most iconic attractions are:

• The Northern Lights (Aurora Borealis) – In Swedish Lapland, especially around Abisko National Park and Kiruna, visitors come from around the world between September and March to witness the shimmering green and purple curtains of the aurora dancing across the Arctic sky.
• Stockholm and the Archipelago – Sweden's capital is spread across 14 islands connected by elegant bridges. Visitors flock to wander the cobbled streets of Gamla Stan (the Old Town), visit the Vasa Museum to see the remarkably preserved 17th-century warship, and explore the breathtaking Stockholm Archipelago with its more than 30,000 islands, islets, and skerries.
• Gotland and Fårö – Beloved for their medieval charm, dramatic Baltic coastline, and extraordinary geology. The UNESCO World Heritage town of Visby draws history lovers with its medieval walls and churches, while the raukar (limestone sea stacks), fossil-rich beaches, and rugged coastal landscapes of Gotland and neighbouring Fårö are a magnet for photographers, hikers, and fossil enthusiasts. If you have limited time, this is the area to head to first!

Other famous Swedish attractions include:

• The Icehotel in Jukkasjärvi, rebuilt entirely from ice and snow each winter.
• Abisko National Park, renowned for hiking and Arctic scenery. Photography buffs will love the scenery. Every frame is natgeo worthy!
• Dalarna, home of the iconic red-painted Dala horse and traditional Swedish culture.
• Sweden's famous fika culture—coffee and pastries—which many visitors happily adopt as a daily ritual. You will be getting up early just to head back to your favourite new coffee haunt. 
• The Göta Canal, often called Sweden's "Blue Ribbon," which stretches across the country through lakes and locks.

After a morning of fossil hunting along the Baltic shore, there is only one sensible thing to do: stop for a proper Swedish fika. A hot coffee, a cinnamon bun... Så gott! (So delicious!)