London...fascinating but expensive
Liverpool...if you're a Beatles fan
Munich...a very interesting city
Rome...incredible,incredible,INCREDIBLE
Naples and surrounding areas...beautiful beyond description
The Isle of Capri...beyond incredible
My biggest disappointment,Ireland (the land of my ancestors).I can easily see why the decided to leave.
Time of year has a lot to do with enjoyment of Ireland. Being a maritime climate, late summer to early fall will give you the greatest likelihood of sunshine. Where you are matters, there are gorgeous parts of Dublin and grubby parts of Dublin. Dublin 4, Ballsbridge is very nice and where I always set up base when I went.
But, it's the country outside of Dublin that's the attraction. The highway down to Bray and eventually Waterford can be stunning, cliff top along the Irish Sea. If you golf, the Curragh. Out to Howth Head, a few castles, Dromoland, others.
What really spoke to me was going up into the hills and mountains of County Wicklow and visiting Glendalough, though. Ireland is gorgeous if you see it in the sunshine at the right time of year. Every shade of green imaginable and then some. The south of Ireland is very nice, too, Cork and environs.
Don't let one disappointing trip turn you off of Ireland, in other words.