In a large saucepan, combine water, cinnamon sticks, allspice, cardamom, and lemon. Bring to a boil over medium-high heat. Reduce heat to medium, and cook for 10 minutes. Remove from heat, and add tea bags. Cover, and steep for 5 minutes. Strain tea into a large pitcher. Add sugar and lemon juice, stirring until sugar dissolves. Serve over ice. Garnish with cinnamon sticks and lemon slices, if desired.