What is the fine-grained topic of the following text: We cannot forget Casa Batlló and Casa Milà, also known as La Pedrera, from which you will also be able to know their history with the tours Barcelona Gaudí: Artistic Barcelona including Sagrada Familia and Casa Batllo and Artistic Barcelona: The Best of Gaudí. Only return the topic.
Gaudí's architectural works in Barcelona and associated tours