Aha...you are there :)...this is my absolute favourite beach on the island: my secret beach. It actually consists of two beaches next to eachother. It can only be reached after driving over a dirt track and you will not find this beach on most of the road maps. It's going to stay our little secret. It's defenitely worth the trip. This is one of the most quiet beaches on Mykonos, and there have been times that we were the only visitors. It's also a good, clean beach, without the usual rubble you find on some of the deserted beaches. There are no facilities like a restaurant or a hotel yet, allthough in 2005 there was construction work going on. They seemed to be busy building an apartment block. In this place it feels not just like you are on another island, it seems more you are on another planet. This is my secret ;)...
Update 2009: so this was the last of the really totally unspoilt beaches of Mykonos and we knew it wouldn't last for ever. In high speed new houses are being built on the hills surrounding the beaches of Mersini and Fokos. Also on Fokos, which used to have only one house on it, the taverna, it has changed. It looks more like a small village now than "the end of the world".
See the difference in the old pictures (below) and the new pictures (above).