I believe perf12 has summed this up nicely.
I can't read the address but would expect it to be in Greece.
I used to have a number of covers like this with this combination of an Austrian Post Office stamp applied in Crete and a Greek Hermes Head stamp applied on the island of Syros (Greek post office #67).
An Austrian Lloyd steamer would deliver the cover to the Greek post office on Syros which would forward it to its destination.
For much of the nineteenth century Syros was the shipping hub in that part of the Mediterranean.
Here's an earlier, pre-stamp cover that I still have in my collection that was sent from Crete to Marseille again via Syros and then on to Trieste etc:
I've posted this cover here before so I won't repeat the routing details but they are in the following thread which might be of interest if you haven't seen it before:Austrian offices in Turkeyhttp://goscf.com/t/57575