The opening at Henley Park, Whiston, is the culmination of the year-long government-funded programme to create 13 new play spaces across the borough. A further 15 sites will be created in the coming year.
The Knowsley Pathfinder programme is the first Wave 1 scheme on Merseyside - and one of only three across north-west England.
The Play Pathfinder local authorities each receive an extra £1m of government funding on top of the £1m already pledged through the Department for Children, Schools & Families' £235m play programme. 2020 Knowsley, which is a joint-venture partnership between Knowsley Metropolitan Borough Council and consulting and business services group Mouchel, has worked on designing and delivering the scheme.
Landscape architect team leader Mike Porter said: "The best aspect of the project for the team is being able to see large numbers of children enjoying the play sites."
Knowsley council leader Ron Round added: "These play spaces will provide the latest in outdoor, adventurous, natural play.
"Henley Park has already been attracting hundreds of children and families since its installation, which is evidence that this is a much-needed facility."