Ice crystals, being close to equilibrium with water under pressure, are observed from the c-axis direction using a sapphire anvil cell. By decreasing temperature and increasing pressure along the ice I-h-water coexistence curve, the crystal shapes are changed from a circular disc to a hexagonal plate with six (10 (1) over bar 0)facets around -17 degrees C and 174 MPa. This is attributed to roughening transition of the (10 (1) over bar 0) interface.