Tomb Raider Anniversary - Croft Manor Secret #1
The first secret is in the gym room, near the entrance. It looks like a small elephant (which doesn't appear in the image below because I picked it up already).
The small metal poles should be risen, if they are not, check the walkthrough to see how to do this (you need to push the button above the entrance).
Go to the marker #2 and jump on the rock in front of you. Jump to the second ledge and go to the left side.
Then jump to the pole nearby, Lara will use this to jump to the next one.
Jump to the next pole and then to the ledge and seen in the photos.
Jump to the second ledge and move to the left side of the rock.
From there, all you need to do is make a back jump.
And you reached the first artifact (yes it is there if you don't pick it up already).