A fascinating "fun fact" about Jungfraujoch, the "Top of Europe" in Switzerland, is that it is home to the highest post office in Europe, which even has its own unique ZIP code (3801). More impressively, the entire Jungfraujoch railway station—the highest in Europe at 3,454 meters—is built inside a mountain tunnel through the Eiger and Mönch peaks. Construction began in 1896 and took 16 years to complete, requiring workers to blast through solid rock at freezing temperatures. Additionally, the Sphinx Observatory on the site houses one of the most advanced atmospheric research stations in the world; because of its height and pristine air, scientists there were among the first to provide definitive data on the thinning of the ozone layer and rising CO2 levels in the European atmosphere.