I used a "glitch" (when you can travel wherever you want, due to a locked screen) and have encountered a really weird screen.

It is near the secret island (where Pete hid his treasure).
It has stairs, two small volcanoes, a chest and an attack potion.

Do you have any idea how to get there? (It is surrounded by water, so the only way to get there is probably through the stairs but where is the other side of these stairs).

Thanks.