Croatia's pocket-size capital is often overlooked for the sun-splashed Adriatic coast. But these days Zagreb, a Habsburg-flavored city in transition, is in the middle of a creative boom. Surprising museum and gallery concepts have sprouted; chefs are getting creative with traditional dishes; modern architecture is energizing everything from kindergartens to cafés. Fall events include the Urban Festival 11, which this weekend brings multimedia performances to abandoned buildings and public spaces.

—Anja Mutic

1. Visit a museum that isn't one.

The Street Art Museum is an art collective without a building. Anja Mutic

The Street Art Museum has no building, hours, curators or opening receptions—just artists and their ideas. In 2010, the collective's first city-backed project had more than 80 graffiti and stencil artists beautifying the wall that separates busy Branimirova Street from train tracks in central Zagreb. A primary school and kindergarten in an isolated 1970s suburb of Dugave got a colorful treatment just last week. "Croatia's cultural politics went so backwards that we decided to form a collective of citizens who want to make a social change through art," says founder Ivana Vuksic.

2. Take a ride down a four-story art slide.

Zagreb's new sports arena Rene Lisac

The Zagreb Society of Architects just started offering customized tours of the city's architectural highlights, including stops at the closed-to-the-public roof of Zagreb's tallest building and the new sports arena. Upon request, you can see the 19th-century movie theater that was turned into a contemporary dance venue by Croatian starchitects 3LHD. Perhaps most popular—and also available without the tour—is a trip down Double Slide, an art installation made for the Museum of Contemporary Art that features two swirling, human-sized tubes. From $90 for a two-hour tour,

3. Dine on a dish that takes weeks to make.

Klub Gastronomada offers private slow-food meals.

The three owners of Klub Gastronomada are chefs, food consultants and purveyors who travel the country in search of unique ingredients. Try one of their private slow-food meals, which can include meltingly tender ribs from the rare boskarin ox, aged for up to 45 days and roasted at four different temperatures over six hours. Or, take a gourmet tour of Zagreb, with a visit to Dolac Market, a mini cooking class and a two-course meal. Jurisiceva 1,

4. Peek at the remains of people's dead romances.

A can of love incense at the Museum of Broken Relationships

At the Museum of Broken Relationships, founders Olinka Vistica and Drazen Grubisic (a former couple, naturally) display mementos from relationships that have ended. The captioned donations from around the globe—including a can of love incense that "doesn't work" (Bloomington, Ind.) and an iron used to press a wedding suit (Stavanger, Norway)—are funny, poignant, biting, sweet. "We wanted to offer a dignified space for people to talk about themselves and their memories, in this world that doesn't encourage dealing with the past," Ms. Vistica explains. Cirilometodska 2,

Corrections & Amplifications
The home-page and search summary for an earlier version of this article misspelled Croatian as Croation.