I always liked Advent calendars when I was a little kid. They provide a little surprise every morning leading up to Christmas Eve, three weeks of micro-Christmases before the big day. Modern calendars have chocolates, Legos, Playmobil, and all kinds of cool stuff behind those little doors. I used to make simple ones as a kid out of construction paper and Scotch tape, though the element of surprise is lost when you’re the one taping nickels and dimes behind the little paper doors.

Today I still love Advent calendars. I also love architecture, so I decided to make an architecture-themed Advent calendar.

I wanted the calendar to look like a little structure, but I wanted each side to feature a different style of architecture. I settled on four buildings that roughly inspired each side:

• The Temple of Edfu
• The Roman aqueduct at Pont du Gard
• The Mysore Palace
• A Tudor row house

I decided to make the “roof” of the calendar a Planisphere, using a PDF from this generator. I added some index dots on the outer wheel that, when lined up with the current time, will show the night sky on Christmas Eve. Well, for latitude 37°, to be precise. You probably shouldn’t use this thing to navigate.

Another early decision was how big to make this thing. Filament is cheap if you shop around, but print time increases geometrically with volume. My original plan for it to be roughly dollhouse-sized, and thus big enough for Ghirardelli squares behind the windows, went out the window when I realized each side would take about 20 hours to print. So I scaled it down enough for those little Dove Promise chocolates to fit, about 140mm on each side. Total print time, including the roof, base, and all the smaller accessory pieces, is about three days. I’ve made thirty of these, you do the math.

I designed the whole thing in OnShape, which is awesome, I use it for all my 3D design these days. It allowed me to make some modular parts, like the doors and windowframes, and iterate them on each side.

Printing was a bit complicated. One thing I’m proud of is designing the whole thing to print without supports. I hate supports, and so should you. I don’t have an MMU add-on, so I had to print one color at a time and insert filament changes at certain heights, and so I designed around that restiction, too.

The whole thing glues and snaps together, and I made illustrated instructions. Also, a little gift card to print and include if you like.