Romans 10:5-7 (ESV):
5 For Moses writes about the righteousness that is based on the law, that the person who does the commandments shall live by them. 6 But the righteousness based on faith says, “Do not say in your heart, ‘Who will ascend into heaven?’” (that is, to bring Christ down) 7 “or ‘Who will descend into the abyss?’” (that is, to bring Christ up from the dead).
Did Paul believe in the existence of an 'abyss' storing the souls/spirits of those who have passed away? Additionally, did Paul believe that Jesus actually, literally visited that place between his death and resurrection?