Daring,
Are you willing to have Rainbowdash and the others on another adventure? They have a dragon, don't worry, Spike is a good dragon. Tell her Rainbowdash.
there isnt really a way to get rid of it to be honest. its to deep into the forest and having ponies go in there and removing the rubble would be much to dangerous with the wildlife around the castle.
But, do you go to it sometimes?