During the actual viking-attack in Algeciras, the mosques were not spared.
At about 19:19 the Islamic call to prayer is heard and the Muslim says in Arabic that "I witness that there is no Allah". It should be "I witness there is no god but Allah", which is heard shortly after that.
In the establishing shot of the market of the Spanish town the Vikings attach, they show a basket of cayenne peppers which were not brought to Spain until after Columbus's discoveries.
Lothbrok is not the family's surname. Lothbrok is Ragnar's nickname, which translates to something like "hairy-breeches". Bjorn, Ubbe, and the other sons do not share this name. They would go by Ragnarsson until such time they each earned their own names like Bjorn Ironside and Ivar the Boneless, from which time they would be known by these.