This is a great idea for inexpensive holiday decor. You can buy shaped molds at Lee Valley Tools to make these ice lanterns, or you can use an old tin, yogurt container or even juice glass. Just make sure to choose something that does NOT flare in at the top.
Fill your vessel part way up with water, then place it level inside the freezer.
Option: add items into the water relating to the theme of your event. At Christmas you can add cranberries, or evergreen sprigs
Once the first level is frozen, set a smaller vessel inside and weight it down with pie weights or rocks. Add water to the top of the container, and place level inside the freezer.
Remove from the freezer and set-out at room temperature for a short time. The lantern will slide out of the mould once it thaws slightly. Place a tea light or battery candle inside the lantern cavity, and enjoy! I placed several of these ice lanterns along the walkway up to the house for my Christmas party. You can also use the an ice lantern on a table centerpiece (with plate or platter underneath).