Hidden chest (Bastion of the Penitent)
From Guild Wars 2 Wiki
To undig the hidden chests, grab a shovel west of Escape Tunnel. The shovel will despawn if the player is dead, so it is not possible to /gg to fast travel. One can use the ley rifts though or just walk with the shovel.
|1||The first chest is found after digging in the Dirt Pile behind Cairn's Perch on the ground left of the path leading to The Holding.|
|2||The second chest is found after digging in the Dirt Pile west of Death Row and east of Escape Tunnel.|
|3||The third chest can be found after defeating Samarog. From the PoI The Warden's Office go in the south-east corner of the courtyard through the spears to a Speared Corpse. Behind it you will find a Dirt Pile. Dig with your shovel to access the third chest.|
|4||The last chest is a bit hidden behind a broken pillar in the south-west corner of the ground below Solitary Confinement. Go in the corner where you find a small tree, the overthrown and broken pillar next to the open wall. Go behind the pillar. The Dirt Pile is below the ground and is almost invisble. Just dig around until you find it there, still on the flat slope behind the pillar.|