Malta is so small you'd be hard pressed to fit a "mountain" in; Valletta is built on a not particularly high cliff with a deep natural harbour on each side. I'm not aware that it has a name in its own right. The only Maltese town I can think of that's built on any kind of high ground - there isn't much to choose from, after all - is Mdina, and I don't think that hill has a name either.