Flyovers 'fly' over anonymous, grimy spaces. Their users definitively want to be somewhere else. Good reasons to take the lower road and stop awhile are rare but some junctions do try. Where the A127 flyover skims the edge of Harold Hill council estate it passes above car parks, broken pavements, a cycle path that ends in a bin. Retail options include a car wash, a lonely strip of furniture warehouses and the Gallows Kebabs van. What an afternoon of promise. Confounding my flyover prejudices, the Adur Viaduct in Sussex (known locally as Shoreham flyover) recently forced me to ditch the stereotype. While mapping a bike ride between Steyning and the coast, I noted some scary spirals around the A283 bypass and designed an avoidance route. Why confront an urban nightmare when there are swans seemingly bobbing for apples in the river, just a bridle path away? The flyover's location seemed oddly isolated for such a major piece of road engineering but I imagined it still came with the usual wall of sound, the line-up of car dealerships, the KFCs and McDs all brand-waving at the passing traffic, and I decided to cycle elsewhere. This meant my initial confrontation with the superb Shoreham flyover actually took place on a bus. And I was so busy being mesmerised by two vast constructions en route that I felt like a passenger on a fairground ride, suddenly taken unawares and cricking my neck to see what I'd missed. Both of the buildings passed were astonishing in their own way; both originating in the early 1800s but with distinctly different functions. One is built at low level, close to the Adur River's manufacturing heaven; the other at a much higher point above sea level, presumably to be closer to God. The first, Shoreham's abandoned Cement Works, is a set of concrete towers and blocks shouldering into aggressively chiselled land, a mix of industrial architectures from the early nineteenth century to the 1950s. It looms out suddenly, a stark grey monster on a narrow road which is otherwise thick with trees and hedgerows on either side. Made for intensive production activity, the place is now eerily empty. The second looks down from an imperious position on Lancing Hill, a gothic bulk of sandstone ribs and turrets. It stands like a compressed accordion, its silhouette looking proper Harry Potter at dusk, and does in fact turn out to be the chapel for a (seriously unwizardy) public school. It was only after passing these titans that I found something even more unexpected. What a 2D map cannot reveal is the visual reality of a setting. If I had looked more closely at the screen, I'd have seen Shoreham flyover's context, its geometry of nodes and highways drawn within an expanse of green pixelation indicating - greenery. Farmland, woods, fields populated by horses feasting on rich grasses. A raised canopy of roadways erected like an inverted treetop trail, twisting and soaring above lush undergrowth and apparently disappearing into forest. Where are the dumped supermarket trollies and mattresses, the puddles and weeds, the graffiti? The lack of urban tackiness was disconcerting. Delightful enough to warrant a Scouts' nature ramble, how did the place manage to stay like this? Did every local planner vote repeatedly against further growth after the flyover's 1968 construction? Have no entrepreneurs at all tried convincing the county council that what it really needs to pep up this lovely, undeveloped junction is a drive-through casino? The result is surely an oxymoron in motoring - a pleasant intersection. And not a fast food outlet in sight. Unless you count the hay bales.