Between the fringes of the Swedish capital, 90 out of 100 stations contain artwork envisioned by over 100 disparate artists. The politically charged oeuvre inside the cavernous-like underground system was initiated during Sweden’s late-1950s cultural boom.

Paintings, carvings, sculptures, and mosaics sunken beneath the 14 islands that make up Stockholm, have become the world’s longest art exhibition. Moving outwards from T-Centralen in the city center, and expanding approximately 70 miles towards the outer reaches of the commuter belt, the Stockholm metro acts as a continuous journey through five decades of European art history—capturing everything from political upheaval to post-modernism, while simultaneously reflecting Stockholm’s long preoccupation with subterranean culture.

The idea of creating a massive string of collective public artworks in the metro surfaced in the end of the 19th century. Reacting against culture being exclusive to the salons of Sweden’s elite, many felt art should be enjoyed by the by all and available to the public. This sense of moral ambivalence was spearheaded by a new political ideology formed in the 1950s, Folkhemmet or “The People’s Home,” led by the Swedish Social Democratic party.

During a time when most of Europe was still recovering from the harrowing economic effects of the second world war, Sweden was experiencing a collective sense of neutrality and high income tax rates. This meant the Social Democrats had liquid cash flow to fulfill their visions without the restriction of rations. Through the introduction of nationalized health service and welfare for the first time, something of a cultural boom was instigated.

As a result, these social democrats integrated art into the fabric of Stockholm. The metro was a common place for the growing population moving from the suburbs to the city—the ideal place to put these public works. Intended to raise social questions around the likes of women’s rights, inclusivity, and deforestation, the artwork is now seen by 500,000 passengers each day.

Endeavoring to share the rich cultural history displayed across Stockholm's metro system, Expedia launched an interactive platform Underground Art, which allows travelers to take a virtual tour of some of the most uniquely designed stations.

Below, you’ll find a captivating selection of photos inside the cavernous-like gallery, containing works ranging from tall bronze tulip sculptures to a pink underground grotto complete with imaginary archeological findings.