This is a great scheme With a well designed development towards the building of Ancient Rome. Your particular focus on collaboration is great as students will gain a lot from working with one another and it is a key skill that we as educators should try to consider more in our teaching. Be conscious that build day 4 will probably turn into build days 4,5,6, and 7 unless you are going to be building for the whole day. The building soes take considerable time,but it is time well spent. It would also be great to see some explicit lessons on group work skills being taught during the lead up to the project. this will greatly enhance the collaboration within the groups. Well done.