It is there, of course, very solid and real, perfectly preserved, with every jade, jasper or lapis lazuli playing its part in the overall design and after a while you can shade your eyes and take in a vision of shimmering white marble. The light rises in waves from the paving stones, and the squares of black and white marble create an effect of running water. Insight the chamber it is cool and dark but rather musty.

Walk the length of a gallery and turn with some relief to the river scene. The sluggish Yamuna winds past Agra on its way to union with the Ganga. Yamuna emerges from the foothills near Kalsi cold and blue from the melting snows: and then it winds through fields of wheat and sugar-cane and mustard, across the flat plains of Uttar Pradesh, sometimes placid sometimes in flood. Past Delhi where its muddy banks are a patchwork of clothes spread out by the hundreds of washer men who serve the city. Past Mathura, where it is alive with huge turtles: Mathura, a sacred city, whose beginnings are lost in antiquity.

And then the river winds its way to Agra, to this spot by the Taj, where parrots flash in the sunshine, kingfishers swoop low over the water and a peacock struts across the lawns surrounding the monument.