In 1526 the emperor Carlos V decided to build the this palace in the Roman style because at that time Italian architecture was in vogue amongst many influential people. The palace is next to the Nasrid places. It is free to go in and look around. For most people the Carlos V palaces should take around 25 minutes to visit before getting in the queue to the Nasrid Palaces. The Carlos V palace seems slightly out of place at the Alhambra, part of the Nasrid palace had to be demolished to make space for it. Many people would agree that it is a very impressive large building which was a vanity project of Carlos V but it is a pity that it was not built somewhere else and the original buidlings had not been knocked down to make way for it.
In Andalucia there are numerous examples how the Christians stamped their identity on the lands they had conquered. For the most part the original moorish architecture was maintained. Most churches in Andalucia were originally mosques and they were simply repurposed without any major structural changes. In my opinion the Carlos V palace is a ginormous "folly". I have never heard of it being decribed as a folly by anyone else but it does seem to fit the dictionary definition. A Folly is a costly ornamental building with no practical purpose, a building constructed primarily for decoration, but suggesting through its appearance some other purpose, or of such extravagant appearance that it transcends the class of buildings to which it belongs. Follies are deliberately built as ornaments. They are often eccentric in design or construction. It is common for these structures to call attention to themselves through unusual details or form. It is a folly? Who cares, but it will certainly provide most people with 25 minutes of amusement. More info