This is a lovely estate, one of the last remaining properties in the Mérignac gravel area, lying next door to Haut Brion and Pape-Clément. The name Caillou refers to pebbles, reflecting the fact that this was once riverbed, when the river Garonne overflowed millions of years ago. The characteristic elegance and finesse of this wine is attributed to its free-draining, gravelly soil and subsoil. The property is 30 hectares of which 21 are given over to vines, planted at a density of 10,000 vines per hectare.