Originally posted by Burnin Prograde:

Blocks stacked ontop of blocks go quite high. If you're having issues with stability try using the metal reinforced beams

I have tried but there is a limity about 24 units high even using iron beams or thickening the bottom walls the only way is building the tower on a filled groung (by this way on can not have inner space) or building it aroud a tree ( so tree is an undestructible material right stronger than solid rock and iron :D)