Known as Boiler or Book Assembly Island (also called Crater Island) , there is a boiler for making paper and books as well as the log chipper which is where you land upon your arrival (after being dumped from the cart). This island is restricted to Gehn and his henchmen, villagers are barred from coming here. The laboratory was used by Gehn to create his linking books and as his centre of operations on Riven.
There is a copper saturated lake here inside the crater (the crater was probably made by a meteor that once hit Riven many many years ago) as well as Gehn's original laboratory high up on the craters rim. The Maglev (also known as a Magcar) takes you from here to Plateau (or Survey) Island.
There is a footbridge linking Boiler Island to Temple Island, the Maglev link to Plateau (or Survey) Island mentioned above and of course, the Cart back to Jungle Island.
One peculiarity of Boiler Island is that there is a small cave where the frog-like creatures ‘Ytrams’ live.