Plaza de la Trinidad probably is the most relaxing place to spend your siesta in central granada. 150 metres off the cathedral you will find many benches here, cooling shade and a sedative fountain in the centre. Grab a good book, lay down on one of the benches and it's hard not to fall asleep in this calm and peaceful atmosphere.
And if you get too sleepy just go to one of the bars surrounding Plaza de la Trinidad and have a coffee. They all are quite good, considerably cheaper than the nearby Plaza Bib-Rambla and even have a curious, cooling sprinkler above the outdoor seatings. read more