Quibus rēbus cōgnitīs ex perfugīs et captīvīs Caesar haec genera mūnītiōnis īnstituit: fossam pedum vīgintī dīrēctīs lateribus dūxit, ut eius fossae solum tantundem patēret quantum summa labra distārent.
Reliquās omnīs mūnītiōnēs ab eā fossā pedēs CCCC redūxit: [id] hōc cōnsiliō (quoniam tantum esset necessāriō spatium complexus, nec facile tōtum opus corōnā mīlitum cingerētur), nē dē imprōvīsō aut noctū ad mūnītiōnēs multitūdō hostium advolāret, aut interdiū tēla in nostrōs operī dēstinātōs conicere possent. Hōc intermissō spatiō duās fossās XV pedēs lātās, eādem altitūdine perdūxit; quārum interiōrem campestribus ac dēmissīs locīs aquā ex flūmine dērīvātā complēvit. Post eās aggerem ac vallum XII pedum exstrūxit: huic lōrīcam pinnāsque adiēcit, grandibus cervīs ēminentibus ad commissūrās pluteōrum atque aggeris, quī ascēnsum hostium tardārent; et turrīs tōtō opere circumdedit quae pedēs LXXX inter sē distārent.