An underground historical quarry in the Hanbury Botanical Gardens of Ventimiglia (Italy)

This paper concerns with the original survey of an ancient underground quarry located in the internationally known Hanbury botanical gardens, located on the Mortola promontory, 2 kilometers far from the Italy - France boundary. The gardens were established from 1867 by Sir Thomas Hanbury with the aim of acclimatizing several rare botanical species coming from all the temperate climate regions of the world. Many restoration works have been executed, and to this end an extended sandy layer located on the upper portion of the property was used as building material: it was extracted from weakly cemented yellowish sands probably belonging to the top of the Pliocenic Ortovero clay formation. The artificial cave opens up to about 90 m a.s.l. and has a total length of 133 m and a maximum difference in level of 8 m; the total volume extracted is of the order of 1,500 m3 and the internal stability seems guaranteed by some stone pillars. The NE portion of the underground quarry has not been surveyed yet because of the cavity infilling: some testimonies from inhabitants report a possible continuation under the village of Mortola Inferiore. The sand quarry of the Hanbury Botanical Gardens is therefore a cultural heritage with a high tourist potential, even if the site requires further analyses about the geotechnical features of the material aiming at assessing the stability of the underground volumes