Small beauty among the rocks.

Centranthus Calcitrapae is a Mediterranean annual cycle plant, that lives in dry wasteland, but can also be found in walls or rock faces.

 The arrangement of the small, pink flowers, which look like an umbel, is quite characteristic; the leaves on the stalk are greatly divided, but the ones at the base are only dentate; there is not much chance of mistaking it for other plants. 

In 1816, this plant was published in Curtis's Botanical Magazine with a list of various other Valeriana species.  The plant pictured here, identified as Valeriana montana rotundifolia, is now known as Centranthus calcitrapa.  It is a hardy perennial, native to southern Europe.

It is not a proper Valeriana and so it has no known sedative effects or medicinal uses.

I found this specimen in a location near Mahon that has such a peculiar name as Dalt Gibraltar.