Covering 500 acres of landscaped gardens and woodlands that slope gently upwards to the Longside Gallery, YSP does what no inside gallery is capable of doing: by placing art outside, it invites new ways of looking. A field, covered in red poppies becomes literally, a colour field. Now in its 30th year, the park is going from strength to strength.

All the big names of postwar European sculpture are here. They include Elisabeth Frink and her beautiful bronzes - men sitting, sprinting, standing in a formal garden, all the while watched by a trio of white-faced Riace (1986-89) warriors.

Frink was inspired by the pair of pre-Classical Riace bronzes found off the Sicilian coast in 1972, but here, her statues are tense and their motives are unclear. It's possible that, like her figure of Judas (1963) at the other end of the garden, their relocation is humanising them, reducing the scale of their latent violence and capacity for betrayal to one that we might all recognise.

The park also provides space to make connections. To come across Barbara Hepworth's statuesque bronzes, her Family of Man (1970), is to understand the genesis of Antony Gormley's Allotment II (1996), the life-size concrete units modelled on the dimensions of 300 men, women and children that are currently at the Hayward Gallery in London.

Moore, a sculptor whose work is integral to YSP, said that all shape and form was to be found in nature, which is to say that his art was a response to what he saw around him. Younger artists, such as Turrell and Goldsworthy, are not in disagreement with Moore, although their methods frame their ideas differently.

Turrell's Deer Shelter Sky Space, a structure that, once entered, allows the visitor to look up through a large square that is open to the elements, which literally frames the sky: on a sunny day you might see a Magritte float by, all blue sky and fluffy clouds.

The key is the transience of the work.
A different timescale operates with Goldsworthy, currently the subject of a far-ranging exhibition at the park. Branches are encased in drystone-walled cavities and cow dung is splattered against gallery windows to create a translucent wall.

Like Gawain and the Green Knight, the Middle English epic that was composed locally and has recently had a new translation by Simon Armitage (the poet has put little boxes around the park that contain rubber stamps that print out lines of the poem), Goldsworthy's work is so based in the landscape as to be inseparable from it.

All this makes YSP more than a sculpture park, or even a site of land art. It is also a place of live art, and a place where the beauty lies in its essential mutability.

Louise Gray is a freelance arts journalist

Andy Goldsworthy is at YSP until 6 January 2008, www.ysp.co.uk