Ocean organs, secret airports, truffles—what's underground in this coastal country is captivating. Presented with Atlas Obscura.

1. The Museum of Broken Relationships

Visit: Ćirilometodska ulica 2, 10000, Zagreb

When love turns sour, even the most mundane trinkets can spark pangs of heartbreak. That’s what happened when artists Olinka Vištica and Dražen Grubišic ́ broke up, so they did what any ex-couple does with their tchotchkes: They started a museum. After they requested donations, their collection grew to range from teddy bears to a bottle of tears, a Taser gun, and a prosthetic leg. (It’s a long story.)

2. Sea Organ

Visit: Istarska obala, 23000

After World War II, the seaside town of Zadar was in shambles. Construction workers turned much of the coastline into a wall of ugly concrete. In 2005, architect Nikola Bašic ́ redesigned the coast by building a sea organ. Under a flight of white steps, 35 tubes lead to a large, resonating cavity. As wind and waves funnel into the cavity, the steps make random sounds—but always in harmony. It sounds like a melancholy whale.

3. Underground Airport

Visit: Plješevica Mountain

In Star Wars: The Empire Strikes Back, the rebels keep their spacecraft hidden in an underground base. Zeljava Air Base was Communist Yugoslavia’s version of that. On the border with Bosnia, the secret air base could house 1000 people and withstand a 20-kiloton nuclear warhead. It’s now abandoned, but four aircraft exits shaped like warplanes are still carved into the mountainside.

4. St. Blaise Church

Visit: Župni trg bb, Vodnjan

In the sleepy hamlet of Vodnjan, some people have been at rest longer than others. Like in this baroque church, where six preserved Catholic saints are on display. The saints were brought here from Venice two centuries ago during the French Revolution. The reliquary is home to 1,600-year-old paintings, St. Mary of Egypt’s preserved tongue, and what’s believed to be a thorn plucked from Jesus’s crown.

5. Game of Thrones

messicanbeer, Flickr

Visit: The entire country!

What New Zealand is to Lord of the Rings, Croatia is to Game of Thrones. The ancient walled forts, the medieval towns under burnt-orange shingles, the cliffside castles by the sea—much of the show’s landscape is Croatia. See the pastoral landscapes at Krka National Park and the village of Ston, home to an intimidating four-mile, 600-year-old stone wall, considered Europe’s answer to China’s Great Wall.