Where is This in Africa?

You're looking at a UNESCO World Heritage site that has been visited by the Pope, Bill Clinton, George Bush and Nelson Mandela. It's symbolic significance is huge and particularly so to African-Americans. It was built by the Dutch in 1776. You can only get there by taking a ferry from a major bustling city. Where is it?

Here's the answer and more information about this destination.

_{Thanks to Mark Moxon for the use of his image}