I don’t think there is one building that is the most inspiring, but when I have been lucky enough to visit different cities, certain buildings have stood out. Visiting the World Trade Centre Transit Hub - designed by Santiago Calatrava - was a powerful experience, not only because of the history of the site but also because of its clean white structure and its scale in relation to its surroundings. Although not a building, I was inspired by a visit to the marble quarries on a recent trip to Carrara, Italy. The process of carving out the stone was fascinating, and the site acted as a natural gallery. You should watch the short film ‘Il Capo’ on youtube
https://www.youtube.com/watch?v=du9_Kn2y2VA its amazing!