In Sinnoh in canalave city, what is the locked building on the NE corner of town?

Question

If it can be unlocked and entered, how? This is on diamond and I have the nat. dex.

Answer 1

That building is used in the Event used to obtain Darkrai. Unfortunately, there is no way you can open the door without the Event item, which has already been given away.

Answer 2

The house was actually used in an event to get to a hidden island called Newmoon Island, where you capture Darkrai. But i'm afraid you can't open the door anymore without an event item which has already been given away. There are two ways to do it: Use the event item cheat code to get in there or set the date to 2007 or less then the event item will exist again.