Residential towers are common among the elite residences of Salamanca and Segovia. I have used this as a model for a variety of places in the story.

This is the Torreon de Lozoya, on the Plaza of San Martin in Segovia. It was built in the 14th-16th century. Several other palaces are also located on the plaza. Here is another with a much smaller tower.

This is the Tower of Hercules, named for the mythical founder of Segovia. It was first built in the 13th century. It was the residence of the Arias de la Hoz family until 1513 when it became a Dominican convent.

Here is a closer view of the upper portion of the Tower of Hercules.