Brussels felt quite isolated at times. But for isolation I would say a slit trench near suffield at 3 in the morning in -35 degrees. Medman 7, 1989 with Royal Irish battle group. Worst of it was, we could hear the pizza delivery drivers in medicine hat 150 k away over the radio and we were living on compo rations.
Parts of the GR20 in Corsica were awesome. 3 days walk to the nearest road.