Thousands of people have to build that castle for him for years

=> That castle................has to be built for him by thousands of people for years.................
 His parents made him study for his exam
 He was made to study for his exam by His parents .
 

The fire has destroyed many houses

=>Many houses have been destroyed by the fire.
 

. The ancient Egyptians built the pyramids

-> The pyramids were built by the ancient Egyptians