Some are saying underground prison in Greenland.
Interesting! What are the sources?
I think that IF he is alive the President would want him somewhere nearby and in U.S. Jurisdiction rather than in a place run by the Danes. We have Gitmo. Camp David is nearby, but I am not certain if there are holding facilities. Somewhere where FBI and CIA and the DNC cannot reach out and touch him. I have no sources on this at all. Just speculation!