We did the great, memorable Robben Island optional in 2009, as part of GCT's late, but fantastic Cape to Cairo trip. We stongly recommend doing it on your own, substituting it for winery tours, etc. that you can do at home, etc. Note the president & first lady just took their daughters there. Having a former prisoner guide you where he, Mandela, etc. were imprisoned for decades should not be missed.
Our PD in 2009 asked our opinion of Robben Island, and said that GCT was thinking of dropping this optional, which apparently it has done. As we have mentioned in other posts, GCT (not OAT) seems to be deleting world class, not to be missed "Discoveries", e.g. Robben Island, Pompeii/Naples Archaelogical Museum, Pyrogovo Ukraine Folk Villages, etc. These deleted great discoveries were optionals, that, if you were not interested, you did not have to take or be charged for as part of the base trip/extension.
Please keep giving GCT feedback that you want their "Discoveries" to continue. We take these trips to continue in-person learning!!