Welcome to Calton Hill, a volcanic hill rising just beyond the eastern end of Princes Street. It sits between the Edinburgh districts of Greenside and Abbeyhill, and it is one of the best places in the city to stand still and simply look. From up here the skyline unrolls in front of you. You can pick out Edinburgh Castle, the great bulk of Arthur's Seat and the jumbled rooftops of the Old Town. But the hill is not only a viewpoint. It is a kind of open-air gallery, scattered with monuments and buildings, including the National Monument, the Nelson Monument, the Dugald Stewart Monument, the old Royal High School, the Robert Burns Monument, the Political Martyrs' Monument and the City Observatory. In the nineteenth century, Edinburgh pictured itself as the Athens of the North, and this hill was treated as its version of the Athenian Acropolis. That is why so much here wears classical dress. Over the next few minutes we will look at the unfinished temple that dominates the summit, at a tower shaped like an upturned telescope, and at a quiet burial ground below, where some big ideas rest.