Who was responsible for creating the secret tunnel under the sewers of Casterly Rock?

Speaking with Varys during a moment in Season Two, Tyrion reveals that when he came of age that he was put in charge of all the drains and cisterns in Casterly Rock. He revealed later in the series that he added a secret entrance in the sewers that are used to overtake the fortress.

Asked by Darrell Rowe · Last updated 5 years ago · 5.6K views · SOURCE