How do i get into Savannah Mine?

[urban bluff]

as the question asked, how do i get into savannah mine?
cause for me it was block by a barrier (the kind of barrier that's usually used when you don't have enough friendship hearts to go to their room) like do i need to do something first or what? cause my quest says to get into the mine which i couldn't even step close to it

[peak elk]

You need to complete the third altar (Advanced Altar) at the Lake Temple