Shops close and the world stops during these hours, everyone is having la siesta.
In the Roman Empire, people also had siesta, slept for a couple of hours to go on idling more energically the rest of the day. The word siesta comes from the Latin word sexta (Spanish sexta) which means "the sixth hour" (Roman Time).
The habit of having siesta is due to the abundant quantity of food ingested at Spanish meals together with the hot weather. It is attested that biologically, because of the great amount of food eaten, the blood pressure decreases giving sleepiness as a result. Besides, the Tropics between these hours is when the sun heats most and even animals go back home seeking for a place to rest.
2. hey it's 16h, people are sleeping...siesta