At the very crest of the hill, you will find the Old Observatory, the only building designed by James Craig left in the city; it was completed in 1792.
James Craig built other buildings but they all fell down.  
mnli hypothesis: James Craig built other buildings but they all fell down.   premise: At the very crest of the hill, you will find the Old Observatory, the only building designed by James Craig left in the city; it was completed in 1792.