Sa Caixota
Sa Caixota is one of the more unusual Ibizan beaches. It's very long, at around 400m, and the sand is a deep tan, near-orange colour, but it's covered also in sizeable rocks. Because of the difficulty getting down to this beach (a great stairwell leads down to it) it remains relatively untouched and peacefully uninhabited.
Finding Sa Caixota is reasonably easy. Take the road to San Josep, then follow the signposts for Es Cubells, and the turn off for Sa Caixota should be there on your left. Look out for signs to Urbanizacion Vista Alegre.
There are no amenities on the beach to speak of, so pack your own lunch and refreshments. There is very little wind here, and being south-facing, you'll have sunshine all throughout the day, so make sure you pack an umbrella too, as there is little in the way of natural shelter from the rays of the sun.
Swimming is a little wilder here than in more secluded bays, but it is still a pleasant, relaxing experience, and in fact a necessary one, if only to get out of the sun for a little while.