In Naples last week, I fell to thinking about catacombs, the old Waterside station and Bastille. Naples is lovely. We were warned that we were taking our lives in our hands, only travel in taxis the hotel could vouch for, run for our lives if anybody glanced in our general direction.
All nonsense, of course. Wandering the side streets trying to explain by mime that we were looking for the catacombs, a chap gestures to his Fiat and invites us to get in, which we do. He got us there at breakneck speed through a higgledy-piggledy neighbourhood, dropped us off with a cheerful arrivederci.
I hadn't realised Naples had catacombs. Neither did lots of others until relatively recently, when the regional authorities were persuaded to open them to the public.
The young woman on the desk explained that she had been among local students who had forced the authorities' hand by occupying the burial chambers. The students were invited to carry out the refurbishment themselves.
The lighting along the tunnels is both unobtrusive and dramatic; there's a glowing, ornate underground chapel used now mainly for weddings. But the most moving aspect of it all was the thought of youngsters with such a vibrant commitment to saving a venerable exemplar of their city's built heritage.
I was put in mind of the students from the School of Architecture at Queen's, who had spent the previous week in Derry devising a plan for the refurbishment and reopening of the old Waterside Station, designed by John Lanyon and opened by the Belfast and Northern Counties rail company in 1874.
It is a wonderful building, site-specific, complementing the City Walls on the far side of the river. It's been out of action since being bombed twice in the 1980s. Travel to Derry on the train today and you'll arrive in a brick-built egg box ugly enough to make you weep.
A campaign by the rail lobby Into The West for the restoration of the old station has, to the extent that this is possible, captured the imagination of Derry.
Nothing boosted the campaign like the dossier of maps and diagrams, measurements, sketches and film clips produced by the students and presented by Into The West to the city council, the Department of Regional Development and local media. Within days, following months of prevarication, DRD Minister Danny Kennedy (above) announced the station would be restored.
That's not the end of it, of course.
As well as being a genial fellow, Danny is a master of verbal opacity. At the time of writing, an Into The West team of qualified sceptics continues to examine his text.
It would be facile to suggest that the Queen's students have produced a final blueprint.
But they have provided a basis for beginning the process of producing a final blueprint.
They did it in a week. Here in the north, as in Naples, young people are brilliant.
I thought the same thought in the streets of Pompeii, less than an hour from Naples, some of whose mosaics, unearthed from the ash that downpoured and deluged the city in 79AD, are worth the journey to Italy on their own.
A vast, exhilarating depiction of Alexander the Great in battle with the Persian king Xerxes was made from more than a million tesserae. (Yes, I learnt the word from the guide book). You stand in awe and wonder whether any of the Pompeii citizens frozen forever in the shapes that they cowered in when Vesuvius vomited fire from the bowels of the earth and entombed them ever stood in awe and wonder before the same enhancing work of art.
There were scores of youngsters in the amphitheatre, sitting along the tiers of sandstone, when a woman, English I think, walked into the centre of the arena, looked around, clasped her hands to her head at the majesty of it all, spread her arms and, in a not-bad voice, struck up O Sole Mio.
At the end, applause tumbled down the steps and lapped all around her.
Pompeii was a hit for the breakthrough band of 2013, Bastille. I happened on them at the British Museum last year against the background of an alcove of gold and purple and orange and red mosaic.
They sang: "We were caught up and lost in all of our vices/ In your pose as the dust settles around us/ And the walls kept tumbling down/ In the city that we love/ Great clouds roll over the hills/ Bringing darkness from above/ But if you close your eyes/ Does it almost feel like/ Nothing changed at all?"