Landmannalaugar is the place that springs to mind whenever I think of Iceland, if only because the weirdness and diversity of its landscapes, to me, has come to signify everything that Iceland is.
We managed only a one-day trek, but even then we found ourselves walking through everything from meadows to volcanic rock forms and sulphur fields, all the while with the colourful rhyolite mountains as a backdrop.
As is expected of Iceland, the weather was frightfully indecisive the day we were there, and it wasn't till almost the end of the trek that the sun made up its mind to stay. And what a difference it made to the scenery! It made the contrast between the white of the snow, the blue of the sky, and the peculiarity of the mountains pop even more than before.
Definitely a place I could visit over and over!