naturalplaygrounds.com tunnel and bridge ~ great resource
Ontdektuin SKA-kinderdagverblijf Plons
Montessori East, Pre-School, Bondi, Sydney, New South Wales As an alternative to highly priced, fixed use plastic equipment installations, timber and other natural materials are cheaper and can be used to craft physically challenging open ended play items, that can also promote spontaneous creative and imaginative play.
Kids: we have a tunnel like this at school playground and the kids love it. The school one is built from a large concrete pipe