Similar Architecture

Much of the architecture that was used in the Lord of the Rings films reminds people of the architecture of the Middle ages. The photo I have included is one of Minas Tirith in the films.

Questions:

1.How is this castle/city similar to the things we find in history books?

2. Why is there a wall surrounding it?

3. Why was the city built this way? Can you think of any historical examples that are similar? What are the reasons for those places planning?