Cabbage Down is a sub-complex of the Cabbage Research Institute near the settlement of Big Cabbage which is characterised by high security and an uncompromising attitude to non-authorised visitors, or indeed anyone just hanging around nearby. Do not go anywhere near it with an iconograph.
The reason for this very sinister corner of a research complex most right-thinking people would view as moderately sinister or at the least, disquieting, is that Cabbage Down is jointly funded by sensitive commercial backers and by military interests. Its purpose is to research the offensive and militaristic applications of brassica. What goes on in there is a tightly-guarded secret and rumours abound, but it is believed that a programme of cross-breeding of selected flora is under way involving taking the livelier native strains of brassica, and crossing them with imported examples of Discworld flora such as the Sapu Tree, the Accelerating Bamboo, and the Sledge-Hammer Shrub, for unspecified purposes believed to be connected to biological warfare. Ecologically-minded objectors in Ankh-Morpork and elsewhere are trying to amass evidence, and are intending to present protests.
To the formerly officially denied British biological warfare research unit at Porton Down, which, while it is now admitted to exist, still does not appear on Ordnance Survey maps. Perhaps Cabbage Down has its Area Fifty-One, or even in local conditions its Area Fifty-Seven... There was, of course, the top-secret American base at Greenham Common, which had a similarly disarming bucolic-sounding name straight out of The Archers, but which farmed nuclear weaponry for possible export to Russia.