Sentence:  The original family who had begun to build a palace to rival Nonesuch had died out before they had put up little more than the gateway, so that the actual <WSD>structure</WSD> which had come down to posterity retained the secret magic of a promise rather than the overpowering splendour of a great architectural achievement. 
Meaning of the word marked with <WSD> tags:  A cohesive whole built up of distinct parts.