...the prison is on the island.
Robben Island
Robben Island is South Africa's most secure prison.
Robben Island was named a World Heritage site in 1999.
If German in origin it means "island of the seals", as Robben is plural for seal..
Robben Island is Dutch for "Seal Island". Obviously you see seals there. In this case the Cape Fur seal.
Robben Island
in robben island
Robben Island is about 5 miles (8 km) offshore of Capetown, South Africa
because there are seals there
it is a prison
The great and remarkable Nelson Mandela was in imprisoned in South Africa.