Very Complicated Chemistry related question

Ok, lets say i had a Cube Rite, its inside was 3x3x3 Meters... (27m^3). And for a hypothetical it had a border 1 meter thick of super strong material surrounding it, to make sure it could not break or be altered in any way possible.

Then i filled the whole inside of the cube with water, the whole 27 cubic meters...

Then I froze the water.

Since water expands when it is frozen and the cube cannot change shape (unalterable, superstrong material) what would happen to the water?

Most liquids freeze at a higher temperature under pressure because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: water freezes at a temperature below 0 °C under a pressure higher than 1 atm. Consequently water also remains frozen at a temperature above 0 °C under a pressure lower than 1 atm. The melting of ice under high pressures is thought to contribute to why glaciers move. Ice formed at high pressure has a different crystal structure and density than ordinary ice. Ice, water, and water vapor can coexist at the triple point, which is 273.16 K at a pressure of 611.73 Pa.