WordNet records no synonym and no antonym for silk road. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an ancient trade route between China and the Mediterranean (4,000 miles); followed by Marco Polo in the 13th century to reach Cathay
Synonyms, antonyms and the broader and narrower relations for silk road come from Princeton University’s WordNet. Full sources and licences.