Hard cover book for a 4 year old that feels special

I've bought my 6 year old nephew 'The Lego Book' for Christmas. It's a big, hardcover book with lots of pictures. His sister is at the age where she wants what her brother has, so I'm trying to find a book that is equivalent for her.

Ideally it would be a large, hardcover book with lots of beautiful pictures for her to look at. I want it to feel special, like something she can spend a lot of time leafing through if she wants to.

Her interests are Rocks and Animals but she is very curious about the world in general, and loves art.

When I was a kid someone bought be a huge anthology of Roald Dahl stories and even though I was too young to understand 90% of them I still adored it because it felt really important and grown up. Importantly though, it was very pretty. So I think nice aesthetics would be a big selling point here.

Any suggestions very much appreciated!