Like an elegant, spidery hand reaching down and helpfully lifting the deck of the bridge up off the traffic, the cable "fingers" of the Taney Bridge in Dundrum descend from a soaring pylon. The resulting lofty structure, forming a gateway to the south Dublin neighbourhood, looks almost ostentatious. Yet its form follows from strict functional requirements. That's the beauty of certain bridges; the elements, and the whole, of the built form express the maths behind their construction (without showing off too much and reaching far beyond the sums of their parts). It's possible to see how all of the bits play their part in holding up the structure: here's the arm offering support, and here are the strings that are pulling up the deck. It is not possible to see the support structure of many buildings, which is why bridges can be so pleasing to look at. There's a place in our hearts for the Clifton Suspension Bridge in Bristol, England by engineer Isambard Kingdom Brunel, who also built many expressive-but-functional iron structures; viaducts worldwide; and the Golden Gate Bridge, which has become a symbol for San Francisco.

