Hi Tiffy
the address is actually on most recent models of satnav or look for street name Vereda De Lorca A Cartagena which is the name of the road just outside the gates and in the district of Murcia postcode 30840.
For the record the actual coordinates are N 37.72428 and W 1.34726 which will take you inside the gates to Al Kasar.
Hope this helps
Gabe