The German town of Gengenbach takes Christmas very seriously. So seriously that it counts down to the holiday with one of the biggest Advent calendars in the world.

Two decades ago, the town of 11,000 people on the edge of the Black Forest set out to bring in more tourists during the holiday season. So to make its holiday market unique, Gengenbach began turning its town hall into a building-sized Advent calendar.

Now one by one, every night from November 30 to December 23, the windows of Gengenbach’s Baroque city hall light up with artistic creations inspired by a yearly theme. At 6 p.m. each evening, the lights of city hall go up, and a spotlight trains on one window. Then, the window shade pulls up to reveal the new window. By December 23, all the windows are open and on display, and will stay that way until January 6.

Hubert Grimmig, Kultur- und Tourismus GmbH Gengenbach

Each year, the windows are decorated according to a theme, like children’s books or the work of famous artists like Marc Chagall. For 2017, all the Advent calendar windows are filled with illustrations by Andy Warhol.

According to Guinness World Records, it’s not the absolute biggest Advent calendar in the world. That record belongs to a roughly 233-foot-high, 75-foot-wide calendar built in London’s St Pancras railway station in 2007. Still, Gengenbach’s may be the biggest Advent calendar that comes back year after year. And as a tourist attraction, it has become a huge success in the last 20 years. The town currently gets upwards of 100,000 visitors every year during the holiday season, according to the local tourist bureau.