I might have paid more attention when I visited Ravenna, some years ago, if I’d known the part it played in J R R Tolkien’s imagination. On that visit, even locals were bemoaning the heat. It took a spectacular storm to bring some relief, but I am ashamed how few of the city’s cultural attractions I saw, preferring to sit in the shade of the square. On the only day of my life I have spent lying on a beach under an umbrella, I was miserable, covering myself in a towel and a copy of a Sunday newspaper, to keep the rays at bay.

Not that I imagine Tolkien lounged around in his swimming trunks, feeling pasty and plump beside svelte Italians playing volleyball or strolling the invisible catwalk that was the water’s edge. As a new discovery suggests, he was more likely to be found, Baedeker in hand, exploring its cathedral or mosaics. This is because Ravenna has been revealed as the model for the vertiginous castle-city of Minas Tirith, in The Return of the King, the last volume of The Lord of the Rings.

Tolkien described his imaginary outpost as “built on seven levels, each delved into the hill, and about each was set a wall, and in each was a gate...” So eerily magnificent does it sound that this summer a band of nutty architects and fans launched a crowd funding bid to reproduce Minas Tirith in the south of England.

Ravenna’s role in one of the most popular novels ever written was discovered when a map annotated by Tolkien was discovered in the private belongings of his illustrator, Pauline Baynes, who died in 2008. In his brusque notes, he explained that Hobbiton was roughly at the latitude of Oxford, and the bottom of the map equivalent in location to Jerusalem. He also indicated roughly what flora and fauna would have been appropriate for each area, using the tone of a Captain Mainwaring explaining a simple field exercise for a platoon of low IQ and flat feet.

Seeing the enchanting pen and ink map Baynes then composed was a reminder of how many hours I spent poring over this magical landscape, and many others like it, as a child. In those days, a novel came to life if it had a map. Never mind that Treasure Island began with Robert Louis Stevenson’s attempt to beguile his future stepson on a wet summer’s afternoon. Sometimes a map alone was sufficient entertainment for a sodden Scottish weekend. There were drawerfuls of Ordnance Survey maps in our household, thanks to my father, but although reality was an adequate substitute for fiction, back then nothing compared to tracing imaginary journeys in fantastical countries.

Made-up places hold less interest for me now, but proper maps have taken their place. One of my complaints about modern fiction is that so much of it comes without clear directions. It might be a reflection of my own appalling sense of north, and equally poor geographical knowledge, but a book can be almost ruined if I cannot locate the action, or see where one country borders another. Something many novelists do not fully appreciate, is that while the routes their characters take might be easily envisaged by them, readers not only need a bit of guidance, but lose heart without it.

For the original map makers, their work was almost as much a piece of fiction as anything Baynes and Tolkien created. Early depictions of Scotland by the likes of Gerhard Mercator are evidence of inspired calculation rather than a scientific rendering of land exactly measured and scaled. As such, it is Scotland as dreamt and hoped, rather than as it was.

Those early years of mapping were a period of almost heroic speculation, a time when geographers, as they sometimes called themselves, were as competitive as mountaineers striding towards a summit. Perhaps the almost wholly speculative origins of maps are the reason why even those that today are accurate to the millimetre still hold such allure. Obviously they are a guide to what is real, but between contours and place names and rivers and woods there is still space for our imagination to roam.