In Norway, people celebrate the summer solstice with this enormous bonfire festival

June 21st - the summer solstice and the longest day of the year - marks the official start of summer.

In Norway, people usher in summer with a massive celebration called Slinningsbålet.

It's celebrated with a huge bonfire every year on June 24th in the town of Alesund, which sits on the west coast of the country.

Slinningsbålet is part of the midsummer - or sankthans - celebrations, which honor the birth of John the Baptist.

Since this time of year marks when the sun starts to retreat, the midsummer fires - which date back multiple centuries - are believed to reflect the sinking flame of the sun.

To celebrate, the town builds a bonfire. But this isn't just your average bonfire. It takes 30 to 40 people several days to build a huge tower of wooden crates that's eventually set on fire, creating a massive roaring fire.

In 2010, the tower was a record-setting 132.71 feet tall. This year, the tower will be 112-feet-high.

The flaming tower is built on a small piece of land that is surrounded by the ocean so when it topples, it falls into the water and doesn't present any hazards. 

Here's a video that shows the building, lighting, and burning of the tower from 2010.

 The tower was not nearly as high last year (only 131.2 feet). Here are some photos of it that were taken by a drone.

And if you're wondering how exactly they light this huge tower on fire, here's your answer: Someone lights what appears to be a fuse housed in a barrel placed at the very top of the tower, and then climbs down as it start to burn. In the photo below you can see one of the climbers lighting the fuse.

And here they are climbing down the tower as it starts to burn.

One of them actually climbs back up to place the burning fuse back into the barrel.

The climbers quickly and safely make their way down before this happens.