In the phrase estas antiguas ruinas, the meaning of the word antiguas is ancient.
Estas antiguas ruinas is a Spanish word and the word simply means These ancient ruins. The meaning of antiguas in the Spanish word is ancient.
Antiguas means ancient. This means something that is old, or having lived or existed for a long period of time. Ancient times means an era that occured in the olden days or a very long time ago.
Some of the words that can be used to replace ancient that is the synonyms of ancient include primitive, former, earliest, primeval, past, etc.
