Both aspects are tricky. In designing a building, experts must take into account a disconcertingly vast range of factors: the makeup of the local soil, the desired height of the individual structure, the strength of the materials available, and the geometry, to name just a few. Then, to turn the paper plans into reality, they presumably face equally byzantine difficulties making sure that all the different tradesmen and machinery do their job the right way, in the right sequence, while also maintaining the flexibility to adjust for unexpected difficulties and changes.
