Every year, our "at school" children have two weeks of Christmas vacation followed by Project Week, time spent working at home. The high schoolers write research papers, 7th graders report on an endangered animal, and 8th graders like Marianna construct a medieval town, castle, or cathedral.
The students are supposed to spend at least thirty hours on their projects, and our 8th graders always do! Usually the last few hours are late, late, late the night before returning to school. Marianna worked hard and Len assisted with management coaching, so the final Sunday was not too painful this year (our family's fifth medieval project).
Some materials decisions: plaster walls, paint mixed with sawdust for grass, dried grass for thatch, and glycerin soap to fill the well.
After searching the archives, I found Joe's castle from January 2012:
And Daniel's from January 2009: