Board Thread:Spoilers!/@comment-5821891-20140317041016/@comment-32390199-20140323100617

Maybe the Tower was enchanted in that way that it couldn't be taken along with the first curse. Wicked may have put her own protection spell on it (as I am sure Zelena is going to take the role of the witch). Similar to how Cora did it, only it would also keep Rapunzel inside.