Abandoned house

Hello

The house next door to us have been abandoned for about 20 years and we would like to buy this but haven't succeded. The owner of the house have deceased many years ago (no one can find his name or know who he is) and he bought it when it was newly built, but in the "registro de la propiedad" the original building contractor is named as the owner. We have contacted a lawyer who have tried to contact the original building contractor but they are not interested in this.

So the question is what options do we have?
I builder told us we should just go in and start using this house (it's wall to wallwith ours) because after 10 years of using it you can claim the property, is that correct?

But we would prefer to just buy it and do it the "right" way but it seems impossible. Our problem is also that there is a bad smell from this house that we sometimes fell when we are using our terace.
So please, any advice woulde be appreciated.

Neither the house, nor the door makes any noticeable response. Examine the door?

DarkLies, its been your turn since he made the post.