You have 5 level of wall, cheapest but lower cost to strong wall but cost a lot. It a Escher Design so just superpose the hightest lvl to the lower level and it like upgradable.
LvL 1-2 need to build manualy LvL 3-4-5 can be constuct by bots!
Tips: watch out the diagonal design! sometime you ll need the right side design and other time the left side design, so be carrefull. I suggest for your first time in creative mode just for understanding how to correcty supperpose the wall design.