Ruins suggest an old and now useless way of life you led in the past, a particular personality structure that has now broken down, or feelings you have held some aspect of your life. The ruins in many dreams are shown as a castle, and this suggests the defences you used at one time to survive, but are now not necessary.
But sometimes the ruins have parts that are still in good repair, and these show you things from the past, maybe even prior to your birth, that are still part of the skills or attitudes you use. Such things often hold family traits or survival skills that have been developed or maintained over a long period of time.
