A funny coincidence that a halo-observer may want to experience is travelling to Egypt and seeing some pyramidal crystal halos.
This odd-radius display was photographed by Márk Laczkó of Budapest, Hungary somewhere over the southern borders of Romania. He was sitting on an airplane heading towards Egypt on 27th October. When he realised they were flying in cirrus clouds, he deliberately started looking for some halo phenomena. The surprisingly well distinguishable 18°, 20°, 23° and 24° halos were visible for about a minute at 06:21 UTC. Unfortunately, there is no documentation or report of a possible 35° halo. The original photo and two other pictures are also available (#1 and #2).