A monument to mark the line of the equator which passes through the Ilheu das Rolhos in the the south of Sao Tom? e Princip?. It was erected after Admiral Gago Coutinho defined the exact location of the line of the equator. Sao Tom? and Princip? is Africa's second smallest country with a population of 193 000. It consists of two mountainous islands in the Gulf of New Guinea, straddling the equator, west of Gabon.