Kastri is a tiny rocky islet off the coast of Kos
and close to Agios Stefanos beach
. It measures just over 150m north to south and just under 150m east to west at it's widest point.
Kastri is around 180m off the coast of Kos, this means it's actually possible to swim from the beach but it's not recommended unless your a confident, strong swimmer, and if you are planning on attempting it then don't forget you have to swim back too.
The more sensible way to get to Kastri islet is by hiring a pedalo or getting on one of the regular boats that takes people over.
Once there you'll find a tiny pebble beach followed by a short climb up to the little blue and white church of Agios Stefanos. Keep going up the rocks and you'll be treated to panoramic views of the Kos coast line and even out to neighbouring islands on a clear day.
The church on Kastri often hosts weddings so is not always open to visitors so check before making your way over.