The Renaissance master's designs for a 'rational' city in northern Italy were never built – but they contain plenty of inspiration for urban planners today, writes architect Alessandro Melis. The word “genius” is universally associated with the name of Leonardo da Vinci – a true Renaissance man, he embodied scientific spirit, artistic talent and humanist sensibilities.

Exactly 500 years have passed since Leonardo died in his home at Château du Clos Lucé, outside Tours, France. Yet far from fading to insignificance, his thinking has carried down the centuries – and still surprises today.