Mark 13:3

And as he sat upon the Mount of Olives
On the east of Jerusalem:

over against the temple:
where he could have a full view of it; the eastern wall of the temple being lower than the rest; (See Gill on Matthew 24:3).

Peter, and John, and James, and Andrew, asked him privately;
apart from the rest of the disciples, they being, especially the first three, his favourites, and very familiar with him.