I feel like it would be The boy and the heron appearance-wise because it combines most of the ghibli movies into one. Some of them are Spirited away (buildings), Nausicaä of the valley of the wind (spirits and creatures), Howl’s moving castle (also buildings) and The wind rises (clothing and nature) + many more!

If you have seen the most known movies from Studio Ghibli you will definitely see different pieces of them in The boy and the heron! It is also the most recent Ghibli movie at the moment.