The giant turtle is a reptile added in Sporkhack, UnNetHack, and dNetHack. It has the unusual property of blocking the player's line of sight like a boulder. Making the turtle invisible (such as with a wand of make invisible) makes it possible to see past it, even with the ability to see invisible.
Several giant turtles are likely to be generated in the Big Room.
The untinned corpse of a giant turtle is very filling, providing more nutrition than a giant but less than a dragon, and can cure stoning, like a lizard corpse. Tins of giant turtle, including home-made ones, are guaranteed to be "delicious and nutritious", appearing as "delicious soup made from giant turtle" and granting 200 nutrition (if not cursed).