A.T. Robertson Commentary Mark 13:3

"And as he sat on the mount of Olives over against the temple, Peter and James and John and Andrew asked him privately," — Mark 13:3 (ASV)

Over against the temple (κατεναντ του ιερου). In full view of the temple about which they had been speaking.

Privately (κατ' ιδιαν). Peter and James and John and Andrew (named only in Mark) had evidently been discussing the strange comment of Jesus as they were coming out of the temple. In their bewilderment they ask Jesus a bit to one side, though probably all the rest drew up as Jesus began to speak this great eschatological discourse.