Secret Spot: Underground Tunnels in Croatia

Picture the perfect honeymoon: sunny beaches, world-class wine, and… underground tunnels? Fortunately, my new husband did not mind a detour through a former bomb shelter on our day trip to Pula in Croatia. A few days later in Zagreb, we heard about another underground passage. How could we I resist? Two Croatian underground tunnels hold subterranean stories ranging from wartime shelters to hosting raves.

Now Entering the Zerostrasse

Pula is an ancient city on the Adriatic coast that boasts many Roman relics, including a Roman mosaic hidden in a parking lot. Somewhere between hunting down that mosaic and touring the Roman amphitheater, I heard about a network of tunnels under the city.

Pula’s built underground tunnels, called the Zerostrasse, during WWI. Pula was an important naval site for the Austro-Hungarian Monarchy, so the tunnels were part of a fortification system created to protect the city, civilians, soldiers, and ammunition.

The tunnel system stretched across the city underneath Pula’s hills. Consisting of passages, trenches, galleries, and communication passageways, it provided shelter from air raids. The two of the largest tunnels were built under the Kaštel and Monte Ghiro hills. Underneath the Kaštel, tunnels with entrances from four different sides connect in a central space.

Map of Pula's Zerostrasse — Credit: Historical and Maritime Museum of Istria

It’s fascinating to walk the tunnels today and picture how the storage areas were once used. While damp and a little wet, the cool tunnels offer a break from the Adriatic sun. Their design offers regular air flow and a temperature around 60 degrees Fahrenheit. Varying from 10 to 20 feet wide and about eight feet tall, the tunnels are more spacious than one might imagine.

Over the years, the tunnels expanded under Italian rule and designated as fallout shelters and emergency hospitals after WWII. Today, Pula’s shelters and tunnels can hold more than 50,000 people, nearly the entire population.

The tunnels also include exhibits by the Historical and Maritime Museum of Istria. On my visit, the exhibit covered the history of public transit in Pula. What an unexpected find and one of the most unique museum settings I’ve experienced! Whether you’re there to learn or you want a shortcut across town, Pula’s Zerostrasse offers a side of the city that you shouldn’t miss.

Underground Zagreb

A few days later and 120 miles away, we enjoyed a stroll on the Strossmayer Promenade in Zagreb’s picturesque Upper Town. We stumbled on the tunnel entrance beckoning in a wall near a park and back underground we went.

The network of tunnels hidden underneath Zagreb’s Gornji Grad or “Upper Town” are shrouded in mystery and urban legends. Grič Tunnel is the only part of this network that is open to the public. Zagreb built it in 1943 to shelter civilians from air raids.

The tunnels fell into disrepair after the war. Legends include tunnels that end below the Croatian Parliament, a bunker in the Sljeme mountain, and use by the Yugoslavian Secret Service. During the Croatian War of Independence, the tunnels became bomb shelters once again. Grič Tunnel also became the site of rave parties as a resistance to the war. In 1993, MTV covered the Under City Rave. As an attendee named Robert said, “We want music, we want peace, and the whole world knows that.”

entrance sign in Grič Tunnel — “Entrance” sign in Grič Tunnel

Grič Tunnel was renovated in 2016 and is now accessible from five different points. The tunnel entrances are marked with the Zagreb coat of arms. It sometimes hosts cultural events like Advent celebrations and historic exhibitions. Grič Tunnel is a quick shortcut through Croatia’s capital city and the site of some handy public toilets. Walking through the 350-meter-long tunnel, you can still see old warning signs posted and imagine electronic music echoing off the walls.

exploring croatia's Grič Tunnel underground

While the underground tunnels in Pula and Zagreb were built as a necessity in the dark days of war, they welcome visitors today with a museum encounter like no other and a unique way to experience these cities.