The Cook Islands are a true South Pacific paradise. However, when travelling that far from Europe, it would be a shame not to leave the main island of Rarotonga. The other island are very charming as well, for example the beautiful lagoon of Aitutaki or the less visited, but lovely island of 'Atiu.
A travel diary of my stay on the islands (during my RTW trip 2008/09) can be found in my blog.