The Alcazaba is an enormous fortress that dominates the city of Almería, standing as it does on a hill overlooking the town and the sea. It was built in the tenth century but over the centuries it has had further enhancements added such as a Moorish palace and, in the time of the Catholic Kings, a Christian palace.
I enjoy walking around the grounds of the Alcazaba and exploring the towers and battlements - especially as I don't have to pay to get in! Entrance to the fortress is free to EU Nationals - just remember to take your passport. The leaflet provided at the entrance kiosk is headed 'Monumental Site Alcazaba de Almería' - a pretty good description because the 'Alcazaba' really is both monumental in size and, I think, monumental in appearance.