The Enhanced Brown-Driver-Briggs Hebrew and English Lexicon has an interesting comment on King Og's couch mentioned in Deuteronomy 3:1. It says perhaps the word couch doesn't refer to a bed, but to Og's sarcophagus (final resting place).
This interpretation actually makes more sense in the context of the verse because no one would say his bed is in Rabbath of the children of Ammon, but they would say that his grave is in Rabbath of the children of Ammon. Furthermore, that chapter is about how Israel entirely destroyed the kingdom of Og. So the only thing left remaining of his kingdom would not be a bed, but his memorial sarcophagus
perhaps transf. to sarcophagus, as last couch עַרְשׂוֹ עֶרֶשׂ בַּרְזֶל Dt 3:11 (v. Dr).
For only Og king of Bashan remained of the remnant of giants; behold, his couch [was] a couch of iron; [is] it not in Rabbath of the children of Ammon? nine cubits [was] the length thereof, and four cubits the breadth of it, after the cubit of a man. Deuteronomy 3:11