A total solar eclipse is set to darken the skies on August 12 in a rare celestial show. To witness this “event of the century” millions of people have been travelling to Spain and Iceland on Wednesday.

The event marks the first time the path of totality has crossed mainland Europe since August 1999. The rarity of total solar eclipses over crowded and densely populated areas has sparked international interest. Therefore, hundreds of thousands of visitors are flocking Spain to join the locals and enjoy this celestial spectacle in its fullest form.

What makes Spain most special during this comic showdown is the occurrence of totality which will take place close to sunset as the Sun hangs low on the western horizon.

As a result, millions will see a dramatic “sunset eclipse” particularly across northern Spain, Zaragoza and Balearic Islands. It will be the first total solar eclipse visible from mainland Spain in more than a century.

Juan Cruz, Spain's Secretary of State for Science expressed his excitement, "I hope that tonight will see the emergence of a ​wonderful generation of astrophysicists. It's such a special moment."

According to Spanish authorities, the country is bracing for 6 million visitors across Spain 's path.

Similarly, Iceland has also been gripped by the eclipse craze as the Nordic country is expecting 80,000 visitors. The path of totality also cuts across western Iceland and eastern Greenland, giving the travellers, visitors and astrophotographers a “a dramatic backdrop of rugged fjords and late-afternoon Arctic light.”

The visitors will experience a narrow path of totality near Iceland’s westernmost coast at 5:44 p.m. (1744 GMT), before the Moon's shadow moves eastward. In the far western areas, the totality will remain up to 2 minutes and 13 seconds while the other cities will witness a shorter period of darkness.

NASA is set to deploy a high-altitude WB-57 aircraft from Iceland to track the moon’s shadow. Other NASA funded teams will launch specialized weather balloons. The purpose is to study how the sudden darkness and cooling of an eclipse affects the lower atmosphere.