Many books have been written on these beautiful buildings, by people more knowledgeable than we will ever be. You go from one room to another, gazing at the extraordinary detail. Each room is covered in either stucco or ceramic tiling or wood.
The stucco or stone is carved into intricate patterns, which do not represent living things (as this is forbidden in the Koran). They are inspired by plant life, and you see many stylised leaves and fruits, as well as pure geometric design resting on advanced mathematics.
Also, there is a lot of Arabic script, highly stylised and flowing. Some of it is quotations from the Koran, glorifying Allah, or citing the revelatory basis for successful conquest or the centrality of water to the design of the palaces. Other scripts are poems, many specially commissioned, exalting the sultan or marking major events such as the circumcision of the eldest son. The picture shows just one small example, where the letters are inlaid into the surround.
Ceramic tiling is brought to a very high pitch here, with complex geometric patterns with colours that often have specific meanings. (In a palace in Fes, to compare, our guide pointed out the blue of Fes, the green of Mecca, the brown of Marrakesh). There is a particular viewing place, a lovely covered balcony called the Mirador de Lindajara ('the eyes of Aixa's house') which has tiles thinner than a little finger and less than the length of a thumb. These are laid out in complex regular patterns, fitted together with precision and grace.
Many ceilings are coffered in ornate wood, one in particular providing an extraordinary stellar depiction of the seven levels of heaven. These were (some still are) heavily gilded. The Christians continued this tradition, and you see many gilded insignia of the yoke and arrow, used by Ferdinand and Isabella.