Normally, hearing a beatbox cover of the Beatles’ From Me to You live would make my toes curl. But the sincere way singer and dancer Žigan Krajnčan retools the song, hitting high note warbles and thudding his chest for extra bass, has me nodding hypnotically.

Skinny and barefoot, with straggly blond hair tied back, Krajnčan is playing a gig with his cellist brother Kristijan at the small wooden theatre-style Layer House venue in Kranj, northern Slovenia. Ranging from beatbox to Radioheadesque orchestral pop, the theatre offers an intriguing showcase of local talent.

Impressive as it is, musical dexterity is not the main reason I’m in Kranj, which has a population of just 38,000 but is Slovenia’s third-largest city. Kranj was declared 2023’s Sustainable Tourism Pioneer by the European Commission’s Destinations of Excellence initiative, which promotes environment-friendly tourism in smaller destinations.

Kranj was rewarded for its initiatives to maintain a fresh, rural feel to the area, which is backed by the Karavankas mountains. In 2016 Kranj was the first Slovenian municipality to launch a bike share scheme that allows users to ride them between towns. Venues have been recognised for cutting waste and using local supply chains, while its Actum Hotel is one of 153 Slovenian establishments given a Green Key sustainable hospitality certificate.

Children are encouraged to monitor their carbon emissions as part of a scheme to lower the emissions of school runs, and the city government’s car fleet was the first in Slovenia to go fully electric. Kranj aims to be officially “climate neutral” soon, having joined the EU’s 100 Climate Neutral and Smart Cities by 2030 mission.

But there’s more to Kranj than framed sustainability certificates. I realise this when Aljaž Primožić places a top hat on my head and takes my photo with a glass photography camera in Inventor Puhar Cabinet, his museum in Kranj’s gentrified old town.

The museum, in an alley among orange-roofed Renaissance townhouses, is dedicated to Slovenian inventor Janez Puhar, who lived in Kranj and invented a process for making photographs on glass in 1842. Inventor Puhar Cabinet also displays a collection of potion bottles, paintings and pump organs gathered from flea markets and skips. Outside, street walls are adorned by works depicting plastic rubbish by artist and environment activist The Miha Artnak.

In pride of place is a glass self-portrait photo of Puhar. “On the internet it says the first selfie was by an American guy in 1839,” says Primožić. “But this was the first Slovenian selfie.”

After visiting Primožić’s curio corner I head to an even more esoteric attraction: Kranj’s network of tunnels, built mostly as bomb shelters when Slovenia was occupied by Germany and its allies during the second world war. Today the big draw among the stalactites and cave spiders is the olm, or proteus: a rare, white, cave-dwelling salamander.

Gregor Alvanćić runs an underground laboratory studying the species, following the work of his father Marko, who founded the lab in 1960. He says that over the past decade the olm’s plight has become linked to Kranj’s wider sustainability efforts, with underground tours highlighting the effects of water pollution. He flicks on a light to reveal two slender proteus gently floating in glass water tanks.

Interesting as these little cave dragons are, it’s the rural surroundings of Kranj that make it worth visiting. The city is known as an “in-between” place, as it’s about 18 miles from both the capital Ljubljana and popular Lake Bled. I find Kranj’s countryside far more beguiling – the eastern lake shore is close to hotel saturation.

I drive up winding mountain roads to the Church of St Primus and Felicianus in Jamnik, about 11 miles west. In summer the lone church, protruding at the end of a sparse arm of rugged mountain, becomes an Instagram hotspot. In the light April rain I have the ridge to myself.

The villages are also where the sustainable restaurants are found. At Gostilna Krištof in Predoslje I eat seven courses of almost entirely locally sourced Slovenian food. It’s high end, but the restaurant is homely and welcoming, serving four courses for €50.

Chef Uroš Gorjanc explains that trout for his sushi rolls comes from a fish farm a few miles away, and that top-class chocolate from Verona is one of the few ingredients he can’t source locally. By using almost exclusively local produce with short supply chains, and scything down plastic and glass use, the restaurant earned a Michelin Green Star.

“We don’t sell Coca-Cola here,” says Gorjanc. “I know the farmers who produce our milk and vegetables … I trust them.”

PR Končovc, a family restaurant on a hillside in Javornik village, is run with a similar ethos by Katarina and Aleš Kristan, who use many ingredients from their own farm. The results are first class, from wild garlic soup to pear-filled štruklji, Slovenia’s doughy dessert. Like Actum Hotel, PR Končovc has a Green Key certificate. To get it, Katarina says, “We even had to change our clothes washing powder. It’s good to be an example for other restaurants.”

Kranj attracts about 60,000 tourists each year, with city officials saying they don’t want the kind of hordes swarming nearby Bled. They also acknowledge that with Kranj having significant industrial output, with companies such as Goodyear running factories here, more sustainable tourism is just one element of the city’s environmental footprint.

Breathing the fresh air on the Kokra River trail running through the city centre, though, it’s clear that Kranj’s certificate pile-up is indicative of positive change. “We know there’s still lots to do,” a tourism official says, adding that the next challenge is convincing restaurants to install electric car chargers. I leave Kranj satisfied, and not just because I have a glass photo of me wearing a massive top hat.