At 1 atmosphere of pressure water will boil at 100C and the boiling point goes up as pressure goes up. If you keep heating water in a confined space it won't boil as long as it remains contained. It would start making steam but the steam would make the pressure go up. As long as the container holds it will just get hotter and hotter, well in excess of 100C.

This is what happens in a pressure cooker. The pressure builds to about 2 atmosphere and the temperature of the water can climb above 100C, cooking your food faster. A pressure cooker is a very weak vessel, though, it doesn't take much to blow the lid off (don't do that). If you had a vessel with thick steel walls, like the boiler in a steam train, you can go much higher.