The last scene shows Lazaro and the friar moving away in a cart on a country road. Despite the story taking place in the XVI century, modern automobile tire tracks are visible on the road.
The time door to 1520 Salamanca is inside a confessional booth in an abandoned church. Confessionals were introduced during the Council of Trent (1545-1563).
During the rescue from the prison transport wagon Alonso uses a modern pistol to shoot the sword from a guard's hand. He then points the pistol at the other guard and orders him to the ground.As this takes place in the 16th century the guards would not be familiar with repeating firearms and would assume that a pistol having been fired would need to be reloaded before it could be fired again.