What is the most valuable doll house in the world?

It's called "Astolat Castle." In 2015, its value was estimated at US$8.5 million.

This castle took expert Elaine Diehl 13 years to construct, between 1974 and 1987.

The doll house stretches through seven levels with multiple staircases, secret passages, and even a wizard's tower that's also an observatory. There are 27 rooms, including a wine cellar and library. With working electricity and plumbing, the castle weighs in at some 900 pounds (408 kg.)

The link below contains a gallery of photos.

https://parade.com/436021/lindsaylowe/unbelievable-photos-see-inside-the-worlds-most-expensive-dollhouse/