Fill an absinthe fountain with ice water.
Pour the absinthe into an absinthe glass and place an absinthe spoon topped with the sugar cube across the rim. Position the glass under a spigot of the fountain and slowly drip water over the sugar cube until the sugar dissolves and the absinthe turns completely opaque.
(You will need roughly 5 ounces of water per ounce of absinthe).
Stir briefly before serving.