Sherden tower.

My next project, while I am building Qadesh and Orontes river, is a Sherden wacht tower.

I am thinking the materials to make the tower.

Found pictures, or information about this people is very, very difficult, but finally I found some pictures about a sherden fortress in Sardinia. Now, the most difficult is how I make it, because is a conical tower, and I don´t know if make with a conical element, sculpt with foam, or make it with corrugated cardboard.

Suggested options?