I need help were is the Solacceon Ruins on pokemon diamond?

Question

i need to know cause i beet the E4 and i am just one pokemon away from 150 and 150 is unknown and its in the Solacceon Ruins & i don't know were it is

Answer 1

go to solacceon rtown go up and u will see trees go to the right then all the way into the corner and jump down the ledges then u will see a cave and thats it

Answer 2

go to the middle and go left to a cave.all pokemon will be unknown and if you have a seal case and you find a boy in there he will go to his house show him a unknown and he will give you the unknowns letter as a seal.

Answer 3

go to solocean town and then go up and go right. jump down the ledges and ull see it.