英语翻译

英语翻译
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The Romans bound their empire together with an extensive system of roads from Rome.Some of these early roads were of elaborate construction.First a trench was excavated to such a depth that the finished surface would be at ground level.The pavement was placed in three courses; a layer of small broken stones,a layer of small stones mixed with mortar and firmly tamped into place,and a wearing course of massive stone blocks,set and bedded in mortar.Some of the Roman roads are still in existence today.And many modern highways follow the ancient Roman routes.