Richard Foster enjoys a family day out at a radical theme park where there was not a white-knuckle ride in sight .

We must stop treating the planet earth as a giant dustbin. This is the message of the Earth Centre, near Doncaster, where £100 million is being spent transforming the slag heaps of two worked-out collieries into beautiful gardens, complete with an assortment of thought-provoking attractions designed to provide an exciting day out for the whole family.

The Earth Centre is billed as a theme park for the new millennium, where visitors are urged to live more sustainable lives to leave Mother Earth in good shape for future generations. But it's also fun.

As a publicity poster for the Earth Centre states: "We want to help people learn how to be environmentally aware and how to look after the planet, but the idea is you'll be having too much fun to notice.

"You might think we are a group of tree hugging, earth loving eco-fanatics, so we have disguised our green ideas as a theme park. Call this devious if you like, but we think it's rather sensible."

Visitors who arrive by car pay more to get into the Earth Centre than those who arrive by a more sustainable means of transport, such as train, bicycle, bus, boat or on foot.

Having blotted my ecological copybook by using the car, I sought to quickly make amends by taking a pedal-powered tour of the site on an Octos, a "bicycle" designed to be ridden by seven people sitting in a circle.

My children, Sophie, 11, Daniel, nine, and six-year-old Rachel, loved the Octos which was steered by Nat, a member of the Earth Centre's staff.

We dismounted from the Octos to explore the Rokkaku Trail which is designed to stimulate our five senses: sight, smell, taste, hearing and touch.

We took off our shoes to feel different textures of stone underfoot and listened to the sounds of the Earth Centre by using the trail's giant ear trumpets, which are works of art in their own right. The trail led to a site earmarked for the Kaki Tree, which is a cutting taken from a tree that survived the American nuclear bomb that destroyed the Japanese city of Nagasaki in 1945.

Unfortunately, the tree has not thrived there, so it has been moved to the WaterWorks building for some tender, loving care.

This building, with its transparent triple membrane, houses the Living Machine, which is part of the Earth Centre's ingenious water treatment system.

The machine is a combination of simple technology and the complex ecology of plants and micro-organisms which work in harmony to clean the centre's waste.

The fascinating bog gardens line the route down to the River Don. Between these gardens, water from the Living Machine meanders through a bio-fence where the green algae gobbles up the waste and is removed to make fertiliser for the gardens.

The NatureWorks building enabled us to explore both land and freshwater habitats while the impressive Planet Earth Galleries - immense limestone-faced buildings built into the hillside complete with a temperature-regulating labyrinth - housed attractions like the disturbing Planet Earth Experience which portrays how pollution is harming the planet.

The play area was very popular with my children and they, like me, were fascinated by the nearby yurt or nomadic dwelling. Its domes gave a great sense of space and tranquillity.

The Earth Centre also boasts a shop and a restaurant which plans to use produce grown in the centre's organic gardens to cut down on the transport of food. What we saw was the first phase of an ambitious three-phase project which is due to be completed in 2002.

Fact file

The Earth Centre, Denaby Main, Doncaster, South Yorkshire. Telephone: 01709 513933

Transport: By car, take Junction 36 off A1M and follow Earth Centre signs. By train, to Conisbrough Station via Doncaster or Sheffield. By water, navigable waterways on the River Don to Earth Centre wharf mooring. By bike, Trans Pennine Trail cycle path.

Opening times: 10am to 6pm until November 7, 1999, last entry 4pm. July 17 to September 5, school holidays, 10am to 8pm, last entry 6pm.

Entrance fees: £4.95 adults; £3.50 children and concessions (under fives free); £2 car park charge.