Out on its famous swan's neck promontory, protected from the land but not the sea, Cadiz is patently a daughter of the ocean. Cleansed by Atlantic spray, refreshed by Atlantic airs, it knows it is different from the rest of Spain; and especially from Andalusia, to which, in the ordinary manner of speaking, it belongs.
Where Andalusian rivals put on a chestpuffing bravura - Seville with its baroque and oranges, Granada with the Alhambra, all of them with carnations in their teeth and a sense of gypsy hair-dos - Cadiz is serious and intent, its 18th and 19th century houses going up and up on either side of straight and narrow streets, the houses themselves as straight as seams on perfectly arranged stockings.
It is slightly dark inside these streets and sometimes marginally claustrophobic, making the old part of town, right out on the promontory, a cool and secret place in summer. In winter it can be a bit of a windtunnel. The modern town, still on the promontory but closer to the mainland, is less extreme in these respects. But an unmistakable sense of straightness underlines the older quarter's fame - for liberalism and humanism, for open-minded rationality: not always leading Andalusian virtues.
Wasn't it, after all, a centre for international commerce, stuffed full of foreigners with interesting and up-to-date ideas, back at the start of the 18th century? As Seville lost its monopoly on trade with Latin America, the palm passed to Cadiz. It started to develop exactly as Seville gave up.
And wasn't Cadiz Spain's leading city for newspaper publishing? Wasn't the great liberal constitution of 1812, which became the touchstone for the modernising aspirations of the nation, written right here, in the lovely elliptical oratory of San Felipe Neri, with Cadiz at liberty while the rest of Spain was laden with Napoleonic chains?
Well, yes, no one could really doubt that version, although it is a little harder to demonstrate that the tradition persists.
But high above the city in his book-lined, picture-stuffed apartment, my new friend Javier Navasques, former city architect, attempts to make the case by comparisons with lesser spots, and allegedly lesser people, elsewhere in Andalusia. He once had a design job on a big ranch, he says, a real, swell, upper-class Andalusian finca, where the bedroom was so magnificent he hardly dared sleep in it. But more than that, his pyjamas, laid out nightly on the bed, were so beautifully ironed he didn't know whether or not to put them on. You wouldn't catch that happening in Cadiz, he says.
Then, rather naughtily, Javier goes on to tell of the private cinema on another finca where the owners were divided from their employees by a glass partition in case the odour of the latter gave offence to the former. That was a generation ago, maybe it no longer exists. But you certainly wouldn't find that in Cadiz, either.
Refreshed with a sense of local superiority, we barrel out into the streets for a glass of manzanilla, the supposedly salt-tasting sherry of nearby Sanlucar de Barrameda. On the way, we pass through a tiny baroque quarter, predating the city of rationalism by a century.
"You have to put the baroque down to the Conde," says Javier. "The British raid of 1596 destroyed everything older in the city." He sounds quite pleased that the man he calls el Conde, which is to say England's very own Earl of Essex, had cleared the way for a nice bit of 17th century architecture.
In early evening darkness, this being January, we popped into baroque courtyards in mouldering mansions, now in multi-occupation. In one of them we counted 22 electricity meters, for 22 families, with plants in pots on every flat surface, the soft scent of washing everywhere and delicate vaulting over the ascending stairways. This is the home of some of the finest flamenco music coming out of modern Andalusia. In the adjoining (baroque) monastery of Santo Domingo monks were once prepared for missionary work in Latin America. "They might have done more good in Andalucia," says Javier caustically.
But the monastery makes the point that old Cadiz really was defined by its relationship with America. There is a small but elaborate image of the Virgin, a replica of an earlier one that used to sail with the Spanish fleet to and fro between Cadiz and the Americas. The younger version has to be content with voyages on the Elcano, the elegant sailing ship used as a training vessel by the Spanish navy. "But the climate change is really terrible for her polychrome painting," says the young friar in charge, appearing at Javier's elbow.
In the end, we have our drink, raising our glasses to El Conde de Essex, somehow skipping Drake, who burned the old cathedral and the first version of the Invincible Armada back in 1587.
Next day, at Javier's insistence, I visit the Women's Hospital, now the bishop's office, to view its brilliant baroque staircase, not huge but dividing and dividing into endless double sets of steps, all under super-fancy stucco ceilings. The hospital chapel houses El Greco's Vision of St Francis, one of the finest works he ever managed. Surprises are there for the taking in Cadiz.
But mostly I spend my time in the Cadiz that I know best and, in the end, enjoy the most, because it is so different from the rest of Spain - the 18th/19th century town and parts immediately abutting. I wander and wander, having endless small adventures.
One morning, the cleaner lets me into the Oratory of San Felipe Neri. The effusive ornament of the chapel, where journalists sat for the debate on the constitution, illustrates the kind of thing the enlightened constitution-writers were struggling so hard against.
I spend a long morning at the Fine Arts Museum. It houses the magnificent set of paintings by Zurbaran for the Charterhouse of Jerez de la Frontera, including a rendering of St Hugh of Lincoln; it also houses the thrilling and often lovely archaeological evidence which proves the city was founded by the Phoenicians, as tradition has always maintained, and just possibly the oldest city of western Europe. (It became a pretty nifty Roman city, too. Their theatre, beside the Old Cathedral, is currently under excavation.)
But it wasn't all high culture, or not, at least, of the purely mental sort. The Cadiz fish market is a wonder - clean, clean-smelling, and loaded with a variety of creatures from the aquatic realm. Naturally, there are fine fish restaurants too.
I had always dreamt of eating at El Faro, one of Spain's top fish restaurants. Finally, this time, I make it: my choice falls on local tiger prawns. In present-day El Faro the prawns arrive in a fresh fruit and mayonnaisy salad, with delicious olive oil followed by a dish of rape - which is to say angler-fish. Words cannot express its essence much better than they can explain El Greco or Zurbaran.
One thing leads to another in both the food and culture line. One day I pop out to Sanlucar, where the Dukes of Medina Sidonia (memories of the Armada) had their palace. There I ate in another famous restaurant, El Bigote, The Moustache. Its (new or newish) upstairs dining-room looks out across the river Guadalquivir to the much-threatened, pine-grown dunes of the Coto Donana. Here it is more tiger prawns and another local speciality, a fish called urta, unknown to my dictionary. Again it is a lunch I'm not complaining about.
I went to El Puerto de Santa Maria, another sherry-producing town, and to Medina Sidonia, a place with a tremendous history and a local belief that it was founded by Phoenicians from Sidon (as opposed to the founders of Cadiz, who came from Tyre). I went to quite beautiful Arcos de la Frontera, perched white as a snowfall on its clifftop. And to Bonanza for the afternoon fishmarket. But every night - who wouldn't? - I came back to Cadiz.