Where is the Art Lover's House in Professor Layton and the Curious Village?

It is not a place just special puzzles you get after you make Luke and Layton happy at the inn. I have added a link to some related questions below the answer. One let's you know which puzzle has furniture in it and has link so take you to the Q/A for those puzzle numbers. Another shows you how to decorate Luke and Layton rooms to make them happy. Look at all of them and it might make you Happy and able to finish the game.

You must find all of the furniture and have Luke and Layton at maximum satisfactory.

Open the trunk. Look at the Inn. The Decorator's House is one of Layton's Challenges.
You must have decorated the Inn for the Decorator's House to become unlocked. Putting the furniture in the correct room makes Luke and Layton happy.