A highway tunnel near Lucerne, Switzerland, built between 1971 and 1976, was originally designed as a civilian nuclear shelter capable of holding 20,000 people. Known as the Sonnenberg tunnel, it was constructed to allow traffic to bypass the city along the A2 highway. Its creation was mandated by a federal law from 1963, which required the Swiss government to ensure shelter for every citizen in the event of an armed conflict. The tunnel features four armored doors, each 1.5 meters thick and weighing 350 tons, designed to seal the shelter in an emergency. In 1987, a large-scale test called Operation Ant was conducted to assess the shelter's readiness. The exercise revealed that it would take 24 hours to close the armored doors, a delay considered too slow in the face of an immediate threat. The test also exposed difficulties in quickly setting up beds for thousands of people. The maintenance costs were substantial, exceeding 300,000 Swiss francs per year. By 2006, the shelter's capacity was reduced to 2,000 people due to cost concerns. While the structure still exists, it now serves a limited purpose. It was used once in 2007 during a protest, and the seven-story command center between the two tunnels has been repurposed for other uses. The original functions of the command center have since changed, reflecting the evolving needs of the region. Recently, the war in Ukraine has sparked renewed public interest in the Sonnenberg tunnel, reminding people of Switzerland’s long-standing civil protection policies. This has led to discussions about the relevance of such infrastructure in modern times, as well as the balance between preparedness and practicality in national security planning.