I can see since the last update a new fifth tower has been added to the 4 towers in this northern part of Madrid. It´s name is Caleido tower. It will be a 180 meter tower (Torre Cristal is 250 meters high) The architects (Fenwick Iribarren and Serrano-Suñer Arquitectura) claim their inspiration comes from Kubricks 2001 A Space Odyssey movie - the monolith on the film.
Credit:
Makespain website
In my view the building contrasts too much with the 4 towers. When the project was presented the images used illustrated a building that seemed almost as high as the 4 towers (perspective played a tricky part on this)