There is a scene half way through "The Tale of the Princess Kaguya" that blew my mind. A little context is necessary though.
Like many Ghibli women, the princess was free spirited. However, she let herself be reformed into a bland and meek woman. She did this only to please her well-meaning but dim father.
Eventually her mind breaks and she runs away. Her expensive clothes fly out from behind her. The formerly restrained artwork becomes wild, thick charcoal lines that jump around. Even the normally static moon shakes in the sky. It was beautiful, and I loved how the style changed to match the princess' emotions.
For me, watching "Spirited Away"[1] was my mind blowing introduction to beautiful Japanese animation and Hayao Miyazaki/Studio Ghibli in particular.
As a child I used to watch a lot of the Japanese Robot related animations. A precursor to Transformers I guess. I also remember 'Kimba, the White Lion' which later got reincarnated as Disney's Lion King. But nothing held a candle to the beautiful animation of Spirited Away.
also very worth watching is yasuo otsuka's joy in motion, his story in of itself is pretty inspiring but also offers a lot of insight into ghibli as well
Visually at least, I think Akira is one of the most visually impressive animated films ever, especially for something made in the 80's when quality standards were much lower