One of the siege camps at Massada in 73 CE in Israel. In the foreground, shadow marks reveal the line of contravallation.

Early in the morning and late in the evening

Clues given by shadows (or shadow marks) are very visible in arid and semi-arid regions. They are, however, more rare in France. Thousands of years of agriculture have leveled out most of the variations in the terrain. Cast shadows reveal only a very few things.

Nevertheless, it can happen that photographs taken very early in the morning or late in the evening in the vast agricultural fields in northern France can reveal very low-relief clues to buried foundations or ancient earthworks.

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Bracquemont, near Dieppe (Seine-Maritime). An overall view of an oppidum, taken on a summer evening against the light.

Feudal mount at Rely (Pas-de-Calais), whose relief is sharply outlined by a raking light.