impassible

[Klimt]

1. Not subject to suffering, pain, or harm.

2. Unfeeling; impassive.

After we discovered this, we never went into ecstasies any more--we never admired any thing--we never showed any but impassible faces and stupid indifference in the presence of the sublimest wonders a guide had to display.

In less than five minutes they had thus revealed to me their characters, and in less than five minutes I had buckled on a breast-plate of steely indifference, and let down a visor of impassible austerity.

[Slava]

A nice fancy word to use in place of poker face.