Make simple syrup by heating 2 1/2 cups water and 3 cups sugar in a saucepan over medium heat until it comes to a boil. Lower heat and simmer 5 minutes. Let cool before using. Any extra will keep in the refrigerator for a month or so, and is good for sweetening iced tea, etc.
Wash, dry and peel the zest from the oranges and lemons, being careful not to take any of the pith. Place in a large glass jar.
Remove pith from two of the oranges. Cut up the fruit and add to the jar. (You will not use the remaining oranges in this recipe).
Stir to smash the fruit a bit, add the vodka, ginger and lemon and seal the jar.
Place in a cool, dry spot, away from sunlight for two weeks, swirling it about occasionally.
Stir in the simple syrup, reseal, and again set aside for two weeks, swirling occasionally.
Strain the liqueur.
Filter it through a double layer of cheesecloth into a pitcher.
Filter a final time through 2 new layers of cheesecloth into the final bottle.