Strabo Geography 3.1.9

[9] Next after [Cadiz] is the port of Menestheus, ¹ and the estuary near to Asta and Nebrissa. ² These estuaries are valleys filled by the sea during its flood-tides, up which you may sail into the interior, and to the cities built on them, in the same way as you sail up a river. Immediately after are the two outlets of the Guadalquiver. ³ The island embraced by these mouths has a coast of a hundred stadia, or rather more according to others. Hereabouts is the Oracle of Menestheus, ⁴ and the tower of Caepio, ⁵ built upon a rock and washed on all sides by the sea. This is an admirable work, resembling the Pharos, and constructed for the safety of vessels. For the mud carried out by the river forms shallows, and sunken rocks are also scattered before it, so that a beacon was greatly needed. Thence sailing up the river is the city of Ebura ⁶ and the temple of Phosphorus, ⁷ which they call Lux Dubia. ⁸ You then pass up the other estuaries; and after these the river Guadiana, which has also two mouths, ⁹ up either of which you may sail. Lastly, beyond is the Sacred Promontory, ¹⁰ distant from Gadeira ¹¹ less than 2000 stadia. Some say that from the Sacred Promontory to the mouth of the Guadiana there are 60 miles; thence to the mouth of the Guadalquiver 100; and from this latter place to Gadeira 70.