The "miniature park" forms part of the visitor centre, but represents the variety of habitats in the wider Nene Park, with a small pond, meadow areas and trees. Volunteers and park rangers worked together to make the improvements, with log piles, new decking to the pond, bamboo chimes, butterfly borders and stepping stones.
Thomas said when he arrived in Peterborough, "the land in what's now known as Nene Park was very bleak and often flooded, while the city had very few public open spaces.
"So my idea was to develop the flood land for recreation, but I didn't have a detailed picture in my mind or the certainty that it would appeal to people on a regional scale. So to see it now, nearly 40 years later, with such good facilities and so many visitors from a wide area is hugely gratifying.
"It wouldn't have happened without the skilled planners, engineers and estate managers at the Development Corporation, the support of the city council, the specialists working at the centre - and now of course all the volunteers."