Thomas Marks.

An arancino is about the size of a shot put. The principal ingredient is sticky, thick-grained rice, starchy and buttery, which cocoons one or other type of filling: for me, that’s ragu e piselli, a daub of mince, peas and gravy that mightn’t be out of place in a cottage pie. The barista hands it over in grease-paper, which is soon glossy with frying oil. The ball has a weight that makes you wonder how it’s been put together, and as soon as you bite through its golden crust of breadcrumbs, it starts to lose its structure: food that wants to fall apart.

I’m in Palermo, the regional capital of Sicily, sneaking from a long-grey London to seek out the kind heat of May. There are wonders of colour and high exuberance here – the gleaming twelfth-century mosaics, the plump, purple aubergines that spill from market stalls, the grinning playgrounds of baroque putti that decorate buildings meant for prayer. It’s the vividness I see first, before my eye starts to attune to the Sicilian shadows. But before long, my overriding feeling is of a city that has settled on the brink of collapse – which is why no street food could be more fitting here than the arancino.

In 1943, the allied bombardment tore up the city. When I walk past the husk of a Renaissance palace, its windows giving on to airy nothing, I’m sure it has stood like this, fragile and abandoned, ever since the war. Ruin is contagious here: even churches that look to have been restored sprout straggles of foliage from high up their facades. Plaster peels from apartment blocks like dry skin. And there’s scaffolding on every street: some of these metal exoskeletons must have been erected decades ago, so far have they rusted into their own wreckage.

I wonder if this city has ever been tidy. I mean that both literally – there are wheelie-bins everywhere, frothing over with trash – and metaphorically, for the city has no obvious centre and its warrens of tenements flake away from three main streets in no discernible pattern. For the visitor, the rubbish is strangely photogenic, like the dilapidated architectural fabric: the look of a forgetful or fallen city.

Palermo turns its back on tourists: immediately south of the Càssaro, the ramrod spine that runs east from the Norman Palace, past the cathedral to the sea, I find myself in a cramped residential district. The streets are just wide enough for small cars – which come in both directions. Washing dangles from almost every balcony and, late in the afternoon, old women smoke on plastic chairs while their granddaughters skip around them. Wherever the street widens into a small piazza, there’s sure to be a clutch of boys chasing after a dusty football. By day and night, I chance on theatrical scuffles breaking out on the flagstones.

And these backstreets have their own backstreets, unpaved, chock with graffiti, seasoned with the odd surprises of abandonment. The porch of a tiny baroque church sealed with a single slab of concrete. Behind some lock-ups, a burnt-out Vespa without wheels, flambéed the colour of treacle. In an alleyway behind the cathedral, a squad of elephant trucks, painted with gaudy cartoon knights – they look like they’re playing truant from an annual parade.

Amid the spate, though, I gradually recognise small local systems of organisation. There’s a updated medieval feel to how specialist shops cluster together: here a row selling old industrial kitchen units or army surplus gilets, there five or six shops flogging opulent cots. In the Capuchin Catacombs, the well-dressed skeletons gurn forward in carefully arranged ranks: the priests and professionals, monks, men, women, and children.

I queue for my lunch at the Antica Focacceria di San Francesco, where the speciality is pane ca meusa. Lung and spleen sandwich. Which tastes faintly like liver, but with a mushroomy smell that you catch on street corners. Another street food that speaks of the streets where it’s eaten: this is a lost off-cut, meat otherwise abandoned here turned to account.

This chimes, I realise, with my slow apprehension that many of these forsaken-looking buildings have been pressed to new use. Inside the monumental Renaissance sea-gate, a bar-cum-bookshop has colonised a cavernous space (the books, appropriately, all slightly foxed or scuffed). And Piazza Garraffello, a ragged square flanked by empty, dilapidated apartments, pulsates after midnight with drinkers and reggae.

Palermo and Sicily keep darker secrets, I know: of the rough contracts of crime, of the seismic vulnerability of the island. They are bound to remain mysteries – though they shadow my precarious sightings.