So now we've answered the first part of this verse:

Rev 17:11 And the beast that was, and is not, even he is the eighth, and is of the seven, and goeth into perdition.

The beast that was - was the Roman empire and the beast that is not (Roman empire no longer in existence, as it was when the temple was destroyed in 70AD).

There are many who believe it's the Ottoman Empire. However, it didn't exist until many centuries later. Besides there's been no temple since 70AD.