DOWN TO EARTH.

The first of the major millennium projects to be opened to the public, this park and natural history centre on old coal workings appropriately focuses on regeneration.

South Yorkshire used to be one of the most productive coalfields in the world, but now most of its pits are closed and both community and landscape have a chance of recovering from the wasteland of pollution and desolation created by the Industrial Revolution. The Earth Centre, near Doncaster, is the 26 acre (10.5ha) core development of a 400 acre (160ha) country park which is being created on the site of two disused collieries. It was the first Millennium Landmark project to open, and has had some of the most varied and thoughtful design inputs of any of the major millennium works. Modelled on the excellent German Bundesgartenschauen, the project is to be a permanent and developing community amenity (unlike the earlier cack-handed British experiments with the idea in the Thatcherite '80s, where the original German system of providing amenities for run-down cities, was subverted to become cheap launch pads for second-rate development).

From the first, the Earth Centre was intended to be the exact opposite of what had been there before: sustainable (not polluting), public (not private), a source of inspiration for the twenty-first century (not a remnant of the nineteenth). A masterplan by the Derek Lovejoy Partnership with Ove Arup & Partners swept away the industrial buildings, remodelled the landscape and started reforestation. Detailed landscape treatment of the core was undertaken by Andrew Grant Associates. The overall aim is to provide diversity by celebrating the natural variety of the site: roughly, to the north soil is acid, made of the waste of deep coalmining; to the south it is alkaline, formed from limestone upper strata. In counterpoint (and sometimes harmony) with this sequence is a north-south sequence from higher to lower, with a grassland meadow zone on the upper ground and gradually, as the ground falls to the now relatively unpolluted river Don, vegetation changes from dry to wet forms. A complex geometry both weaves the different elements together and emphasizes the particular nature of the topography and its chemistry. Descending from the meadow zone are terraces with different plantings, a zone of forest gardens, a wetland area near the river, and these are interspersed with events: a children's play area, an arena and a spiral of coal and limestone which greets visitors as they arrive from the bridge to the car park on the other side of the river. Smaller celebrations of place are created by forming arches, geodesic bowers and tunnels out of timber thinnings (the spindly young trees that are cut out in forestry to allow their fellows to grow large, and which have little commercial value). They are used green (without seasoning) with the advice of Buro Happold who gained experience of such techniques working with Richard Burton at Hooke Park (AR September 1990). In at least one instance, an arch is being made of live willow saplings.

Major landmarks are buildings. Feilden Clegg have produced the gateway: a contrasting pair of structures which form a funnel leading to the interior of the park after you have crossed the Don bridge from the car park or station. To the left is a glass rectangle protected by an outer skin of green oak slats: this is the restaurant, a cheerful airy and luminous place which provides excellent locally sourced food. To the right are the Planet Earth galleries, partly buried in the artificial hill under a flower sprinkled grass roof, and partly exposed as planes of well-crafted ashlar: local limestone which rather unfortunately forms a frame for a trendy and dull graphic welcoming panel -- still, this can be changed, or better still, replaced by something in carved stone. Within, a long toplit space contains a large and detailed model of the Don valley. This leads to subterranean galleries devoted to shows about ecology and its local lessons.

At the moment, the two sides of the entrance are being connected by a solar canopy: a ceremonial timber entrance grove supports a [1000m.sup.2] plane of photovoltaic panels. They will generate 80 000 kW of energy to provide between 20 and 30 per cent of the galleries' total needs.

So far, the other buildings on the site are the Natureworks and the Waterworks. Letts Wheeler designed the Natureworks, an exhibition gallery for water and terrestrial ecology poised over the park's largest pond at the edge of a small coppiced wood, It is an elegant little pavilion, made as far as possible out of standard components on a steel frame structure. Glass and timber cladding were chosen for economy and durability. Unheated, the space is cooled in summer by air from the pool which flows up by convection through the slatted oak floor. Waterworks, by Alsop and Stormer, is another simple steel frame, this time on a purple concrete plinth. It houses the Living Machine, which uses natural processes of plants and algae to purify waste water. It is the centrepiece of a demonstration sustainable sewage and water management system for the whole complex, and the upper part (clad in the Millennium material ETFE) is a viewing gallery of the hydroponic tanks in the plinth. Through them, water is drawn by gravity and progressively cleaned by the vegetation, It is a modest, touching little building by a firm notorious for its gestures.

The big gesture at the Earth Centre is to be the Ark, designed by Future Systems, a very big multi-level exhibition and exposition complex cut into the rising ground to the north of the site and covered with a huge multi-coloured lightweight roof. Again, photovoltaic panels will contribute to energy demands. The Ark is in phase three of the development, which is expected to start at the end of 2001. By then, the landscaping will have begun to settle in, and so presumably will management policies which are intended to increase the approachability of the place for the public.