Simplify the following text for a Grade 4 native English-speaking person.
Original: Agra 's Taj Mahal is one of the most famous buildings in the world , the mausoleum of Shah Jahan 's favorite wife , Mumtaz Mahal .
Simplified: Agra 's Taj Mahal is one of the most famous buildings in the world . It is well known for its reason to be built for Shah Jahan 's favorite wife , Mumtaz Mahal .