The Scottish National Gallery of Modern Art has a Richard Long retrospective.
I've known Long's work for a while and love it. He takes not so much landscape, but the land itself as his subject - mud, twigs, the process of walking. "Throwing muddy water" uses mud splashes on the wall to create a triptych of enigmatic symbols. "A line made by walking" is simply a photograph - in black and white, starkly reductive - of a straight line path made in a muddy field.
There's something quite meditative about these works. The subject is the artist's interaction with the landscape, the soil, the natural materials. We see how the mud has been thrown, squelched, left to dry. There's an element of time; Long exposes natural forces such as gravity, erosion. He opens up, in small, a vista on to geological time and infinite space (it reminds me of the way Tennyson sometimes does this in his poetry, a tiny lyric opening up into a whole universe).
Perhaps it's because his work is to do with time that so many of his works are represented by photographs. They're not intended to be permanent. Their impermanence is part of their meaning. And yet they are strangely permanent, decisive in their effect; a straight line marked on a field, a decision made, which will never be reversed; even when the trodden path has long been eroded, the mark of that work of imagination, that engagement with the landscape, is ineradicable.
For anyone interested in long distance hiking as a mode of spirituality and engagement with the earth, rather than simply an olde worlde way of getting from A to B, Richard Long's work is an essential reference.