As for these things (ταυτα). Accusative of general reference.

One stone upon another (λιθος επ λιθω). Stone upon stone (locative). Here both Mark 13:2; Matthew 24:2 have επ λιθον (accusative). Instead of ουκ αφεθησετα (future passive) they both have ου μη αφεθη (double negative with aorist passive subjunctive). It was a shock to the disciples to hear this after the triumphal entry.