It's easy to assume that when you've wandered round a city's streets for a few weeks, you know it.
But that's not always the case. It is in England, probably. We tend to build our houses on to the street, so the frontage is the main aspect.
Even then there are exceptions. Wander down some of the mews in west London, and you get a different feel from the grandiose stuccoed facades on the squares and streets. This was the built environment of a class-divided society - "the rich man in his mansion, the poor man at his gate," or in this case Milord in his town house and the servants in the attic and out the back in the mews. For some reason I've always felt more at home in the mews.
Edinburgh is quite similar - at least, in the New Town. Fine, tall, uniform, creamy stone Georgian facades on the main street - and hugger mugger single storey garages and sheds and cottages in the alleys at the back. You can walk the whole of the New Town and practically never come out on to the 'parade' streets if you feel so inclined.
But some cultures have much, much less open to view. For instance, you'll never understand St Petersburg unless you go into the courtyards of the big apartment blocks in the centre.
Outside, they're just grey blocks under a greyer sky. And outside, Natasha is just a bundle of warm clothes with a human being buried somewhere in it, struggling against the wind and slushy snow.
Inside, Natasha emerges from her wrappings and becomes a retired art history professor with a graceful presence and a dry sense of humour. And inside, her flat is lined with books and fine porcelain, abstract paintings, and a spotless white carpet makes up for the fact that the snow outside is grey with the dirt of a whole winter.
Russians keep all their best things inside. Perhaps that's at least partly about living in an unfree society; you keep your thoughts to yourself, and you keep you culture to yourself, and you keep anything that really matters inside your own house.
Southern Spain is like that too. Look at the Great Mosque of Cordoba from the outside and you just see a blank wall, divided by big bulky buttresses, with a few finely decorated doors but otherwise plain. It could be a town wall, a garden wall. It gives you no hint at all about what's inside.
That's something you find in Arab culture in the Middle East too. Courtyards become the focus of life - they are cool, they are secluded. No one does anything on the open street. Souks are interiors rather than exteriors; the market happens inside a huge building, a huge set of covered ways, rather than in the open.
So in Cordoba, you can't understand the city unless you understand the way it is shot through with greenness, the way the fabric of the city and its streets has a weft thread of courtyards and gardens running through it. There are a couple of patios (courtyards) which are always shown off to visitors, of course, but by the very fact of being shown off in that way they've become open spaces - they've lost their interior feel.
It's little alleyways like the Callejas de la Hoguera which goes past the Islamic University, or the Calleja del Pañuelo, which still preserve that feeling to some extent. With the Callejas de la Hoguera, there's that interconnectedness between public and private space which is a characteristic of Moorish architecture in Spain - you're walking down the alley, then suddenly you're in the garden of a restaurant - is this public or private? a through way or a back garden? You just don't know.
Cordoba has an association devoted to the patios. At Christmas last year, they opened some of the courtyards and performed villancicos (the Spanish equivalent of carols). In May, more of the courtyards are open and there's a competition for the best gardens.
That interiority, that feeling of seclusion, is what finally won me over to Cordoba. It's a difficult city to know - because all its best sights are on the inside. But it's worth knowing.