Benjamin of Tudela

In general, Benjamin of Tudela is a reliable source for an objective viewpoint during the time period. He is from Spain, which gives him some background with the Islamic faith, as Islam was prevalent there. He is also a rabbi, giving him general knowledge of a monotheistic religion similar to Islam. He traveled frequently, thus was aware of many different opinions and viewpoints. He visited both the places and talked about them from his experiences rather than  other people's opinions. However, he only speaks of the good points of the both Constantinople and Baghdad, like the Hippodrome and the Dar-al-Maristan, and does not address any of their faults, which gives him a small bias.