Source, official ECoC website: https://bodo2024.no/en/
Bodø is the largest city in the Nordland county and the second largest in Northern Norway. However, it's not only the fact that it's a larger town (by Norwegian standards) that attracts large groups of visitors every year. Located just north of the Arctic Circle, Bodø has much to offer all year.
With its 50.000 residents, Bodø is the 12th largest town in Norway. It's seen tremendous growth during the last years, though, and aims to increase the population to 70.000 within 2030.
Since Bodø lies just north of the Arctic Circle, the midnight sun is visible from the 2nd of June until 10th of July. This is a natural phenomenon that attracts large groups of tourists every year. Can you imagine, the sun doesn't set for more than a month (24 hours of sunlight!).
Even though the town is north of the Arctic Circle, there is no true polar night in Bodø. This is because of the atmospheric refraction, which basically means that the border for the polar night is slightly further north of the Arctic Circle than Bodø (you don't need to travel further than to the Lofoten Islands until you have true polar nights). However, the high mountains in the south block the sun so the sun is practically gone from the city between early January to early December.