It is located in the beautiful seaside town of Marsaskala and near to our very good friends L&L.
There are now only four of these fortifications remaining in Malta and would be more than happy for a fellow GCer to place a cache at any of the remaining three.
More information about this historic site can be found at:
http://www.militaryarchitecture.com/index.php/Fortifications/st-thomas-tower-and-battery.html or https://en.m.wikipedia.org/wiki/Wignacourt_towers
Many thanks to zejtunlil for maintaining this cache.