Ok, this question may have been asked a few times already but in this case I couldnt figure it out through the other questions.
And I actually did it and created this thing by merging two landscapes (Blender Landscape Addon), but I literally have no idea how I did it. I just read something about merging and pressed some buttons and it kinda worked. The problem with this model is, that it has very messy geometry, disconnected vertices all over the places. When I try to recreate it, it does not work, because I can´t figure out how I have done this in the first place.
How can you create an island like this, that also could be shown in the foreground? Is there a better way than just somehow merging two landscapes together?