Here is the full list of all 10 Triple Town achievements.
Built your first two-tier mansion using four or more houses
Built your first castle
Created your first treasure chest
Terminated six bears in a single blow.
Built your first mansion
Built your first sky castle
Built your first floating Triple Castle ... the pinnacle of civilization!
Built your first mega-castle using four or more mansions
Built your first mega-sky-castle using four or more castles (yeah, yeah, we know you're good at this!)
Terminated a dozen (12) bears in a single blow.