The palace started life as a fortress, built in 1215 to protect the people who lived on the rock below. Over hundreds of years, each new prince added rooms, towers and beautiful painted ceilings, turning it slowly from a tough lookout post into a grand home. Today the building is a mix of both - strong stone walls on the outside, elegant halls on the inside.
In the summer, visitors can walk through many of the palace's rooms and see real paintings, old furniture and armour that is hundreds of years old. The State Apartments are especially grand, with ceilings painted by Italian artists a very long time ago. Standing in those rooms, you can almost hear the footsteps of everyone who walked through them before you.
The palace overlooks the whole of Monaco. From the square in front of the main gates, you can see red-roofed houses stepping down to the harbour, yachts bobbing on the blue water, and on a clear day, mountains across the border in France and Italy. It is one of the best views in all of Europe.