Candid street shot, London UK.
The traditional hat that Muslim men wear is known as the Taqiyah, which is a raised and rounded skullcap. Muslim men wear this hat because they believe that Muhammad always had his head covered, making it a recommended act for members of the religion today to also cover their head.
Many muslims wear the Taqiyah with pride as a testament to their faith, while others wear it only during their 5 daily prayers.
There are several variations of the Taqiyah depending on which region of the muslim world you are in. For the most part, they all look relatively the same with minor differences and can have a wide variety of colours and designs, with the most traditional and widely used one being a plain white Taqiyah.