I'm an official one with a Blue Badge, trained up good and proper with certificates to boot.
There are less qualified guides; enthusiastic amateurs (occasionally better at the job than many of the 'real' ones) and experts who haven't taken a guiding exam but like to get stuck in.
Then there are the simple cranks attempting to guide for unknown reasons, perhaps lonely folk wanting a bit of company in exchange for half-remembered knowledge.
Outside the Colosseum in Rome on holiday a week or so ago, I rediscovered a type of guide I'd forgotten about: the 'hustler-guide'. We don't have them in Manchester, as we don't have that kind of floating tourism. We don't have an international tickbox attraction outside perhaps Old Trafford stadium.
These twenty something hustler-guides were shouting and competing with each other like market traders selling off bananas that had reached their sell-by date.
They were clearly not official guides and clearly a bit free with the facts. One German sounding guide rushed over and bellowed at me: "Take a tour around the Colosseum, there's a two hour queue to get in and I'll take you straight there! Very cheap deal for your family."
I didn't like the cut of his jib and shock my head. But I sort of admired his passion. When I said no, he was replaced by a another five 'hustler-guides' instantaneously. We were like Christians thrown to the lions...and other Colosseum analogies.
As it turned out our German friend was telling porkie pies in his desperation for the work. It only took us about 35 minutes to get in.
You can tell this by the way some of the chatty ones want to tell you about stuff they've read in the newspapers. Often this revolves around a particularly brutal murder, fire or car wreck, that happened at that junction, in that row of shops, at that roundabout.
They finish it off nicely by informing you that your hotel isn't a safe area and it'd be probably best all round if you jumped back on a plane and forgot about the whole sorry business before you are attacked by the latest immigrant group the driver doesn't care for.
It's a certain taxi-driver's way of saying: 'Welcome to (fill in a city of choice) and we hope you have a lovely stay'.
But categorically not all taxi drivers are like this.
In Manchester we've got several cracking characters, full of knowledge and love of the city - one of them John Consterdine even combines being a qualified guide with being a taxi-driver. A cheery, cheeky chappy - tourists love him.
In Naples, on the same Italian holiday as mentioned in the Rome story, we had just such a taxi-driver guide, albeit an unqualifed one.
Umberto loved his city and wanted guests to love it too. He delivered encyclopaedic knowledge of Neapolitan history down to the types of eruption Vesuvius is capable of and exact population figures of the city. He also had an astute line in political commentary.
What was more astonishing was his ability to deliver the facts while overtaking stationary vehicles at red lights on the wrong side of the road, crashing the red light and then wheel-spinning round blind corners.
It was sort of exciting.
“We are five thousand years old,” Umberto said, while inserting his five-seater cab into an implausibly small gap between a lorry and a bus. "We are the third city of Italy in population with three million but we have the highest density - maybe in Europe. There are one million people living in our downtown area and that is not so large a place."
He's right about that. Those one million live cheek-by-jowl packed in, one on top of the other, in central apartment blocks in an area maybe no broader than four miles by four miles. Perhaps less.
I asked him about the apalling litter and refuse problem that still burdens this most giddily enjoyable of cities and has done for six years now.
Taking both hands off the steering wheel and throwing them up in the air he exclaimed: "It is the Mafia, the Camorra! My city is, as I say, very old, we have seen many things, many governments and kings, but we always have the city. But we have the politicians too. We say ‘You are more likely to find a prostitute who is a virgin in Napoli than a politician who is honest’."
His passion was moving.
“Where did you learn your English, Umberto?” I asked. Umberto was an enthusiastic but inaccurate English speaker with tortured pronunciation.
“Phil Collins. When I was younger I listened to all his songs. He sings very quickly but I learn. And maybe John Lennon helped, but it was more Phil Collins. I have a book too."
He leaned across me and picked out a book from the door compartment. It was a well-thumbed copy of the novelisation of the film The King's Speech. It was a dense book that looked like it may have a little more depth than Phil Collins' lyrics.
Indeed the biggest shock of the journey was to find that Phil Collins had any use at all.
But who cares?
Umberto was a fabulous guide, a concerned guide, great company,an enthusiast.
And either the world’s worst driver or the best - I'm not sure.
We were staying in Naples for the full week holiday.
Coming back from a neat, packed Rome - where we’d been in a queue 200 metres long at St Peter’s - Naples provided a stark contrast.
Slightly disorientated outside Naples Central Station we found ourselves in backstreets in the dark.
There was a Gotham City atmosphere. Almost dream-like. Or nightmarish. Forget Gotham it was more like Yossarian's description in Joseph Heller' Catch 22 of a late night walk around wartime Rome.
In one desolately filthy square a group of Chinese men and women (the only ones I saw in the city) were doing strange formation dancing to a mixed-up, messed about version of Queen's We are the Champions. The square was filthy beyond telling under a shabby skyscraper hotel that looked like it had hosted murder in every room. On its roof was a neon sign flashing red like the blood of the victims.
Then we came to a square patrolled by whores staring with wasted eyes as I wandered past with children in tow.
Almost immediately was a packed pizza parlour with outdoor terraces where the Vespas were stacked like second-hand books on a market stall, kids revving the engines, people exclaiming and everywhere shouts of laughter.
In one particularly ill-lit district a woman, skinny, palpably impoverished, encouraged her – what? – thirteen year old son into a big wheelie bin and then rummaged around with him for any remaining goodies. It was desperate. They were filthy. They looked tired. and given Naples is a very poor city, I wondered what could have been left in the bins that was worth salvaging?
At times like this with the extreme filth of Naples, with the lack of police on the streets, under the failed street-lights, under once magnificent apartment blocks now festooned in weeds, under the broken windows, beneath the buildings with just the odd light on, it felt as though the whole of civil society had broken down. It felt like Naples was a city with no government, a place authority had fled, where a sort of tranquil anarchy reigned. As we waited at one pizzeria all the lights in the whole city district and in every building cut out for ten seconds and then flashed back on.
Naples at night especially in August when many inhabitants have fled to summer towns and campsites is unlike other Western European cities. It is the diametric opposite of, say, Geneva, or any city north of the Alps.
It could be terrifying, but if you are a city dweller yourself, it’s exhilarating too and the sheer love for life of the Neapolitans when you encounter them, their joy in a quick song, in food (if there’s money), in animated conversations somehow glues the whole crumbling, litter-strewn, age-old city together.
This aspect of Mediterranean character and it's difference to that of northern Europe is perfectly expressed in naughty boy poet George Barker's poem The Oak and The Olive.
We got takeaway pizzas that evening. The pizza chef in the restaurant was a whirl of food choreography, making the pizzas, firing them, turning them, charring the base of the pizzas perfectly, putting wood on the fire too. He was a matador of the pizza world, making twenty or thirty pizzas in half an hour single-handedly.
The locals spoke pidgin English to me and I spoke pidgin Italian back. Given the busy Saturday night custom and given it was such a neighbourhood pizzeria, the locals adopted us as exotic foreigners, it was all laughter and half-understood chatter. We were bought rounds of beer.
Naples is a magnificent city. You have to love its humanity despite the filth. I'd love to guide the place.