A good tower is an arresting image. From Babel to Manhattan, from Moscow's Kremlin to the turreted silhouette of the Alhambra in Granada, towers have the power to inspire, to guide or control, or even to provoke.

Many a writer or philosopher has sought solace in a tower. The Irish poet William Butler Yeats spent every summer in a tower near Gort in western Ireland. It became an emblem of Yeats' refuge from the mainstream of Irish society. In Switzerland, Carl Gustav Jung built himself a tower on the shore of Lake Zürich, from which he might ponder both the Alps and the human subconscious. The German poet Rainer Maria Rilke closeted himself in an ancient tower at Muzot in the Valais to pen his lamentations for the lost - eventually published as the Duino Elegies.

From the gaunt cooling towers of coal-fired power stations in the English Midlands to the ivory towers of a hundred universities across Europe, towers are potent symbols of either modernity or tradition. There are functional towers, like airport control towers and lighthouses and fictional towers like Tolkien’s Tower of Ecthelion. There are towers that symbolise faith and identity from minarets in Mostar to church towers in a thousand country villages. And there are towers that attest to secular power like that at Canary Wharf in London’s Docklands.