Alternate world - turnstile in swamp and "flying carpet" snake

[elgatocurioso]

I'm looking for a book that I would have read about 1990.  I'm not sure how old the book was at the time.  It is an alternate reality book like the Chronicles of Narnia.  As I recall on a dry spot in a swamp the children found a turnstile standing alone.  Walking through the turnstile tool them to the alternate world.  Anything metal they were

Comments

[bluemermaid]

I think it's The Dark Green Tunnel by Allan W. Eckert: http://www.amazon.com/Dark-Green-Tunnel-Allan-Eckert/dp/0595089623

I googled some of the words from your post and this one seems to fit. It sounds interesting!