Preheat your oven to 325°F and position one rack in the center and another on the bottom.

For the graham cracker crust, mix graham cracker crumbs, sugar, cinnamon, and melted butter in a bowl. Press the mixture into a 9-inch springform pan.

Bake the crust in the center of the oven for 8 minutes, then set aside to cool.

In a small bowl, combine the ingredients for the cinnamon swirl and set aside.

For the streusel topping, mix flour, brown sugar, cinnamon, and melted butter until crumbly, then set aside.

In a large bowl, beat cream cheese and sugar until smooth. Add sour cream, flour, salt, and vanilla extract, mixing well. Add eggs one at a time.

Pour half of the cheesecake filling over the crust, sprinkle the cinnamon swirl, then add the remaining filling. Swirl gently and top with streusel.

Place a pan with 2 cups of boiling water on the bottom rack of the oven for steam. Bake the cheesecake on the center rack for 70 minutes, then remove the water and bake for another 20-30 minutes.

Cool the cheesecake in the oven with the door ajar for 2 hours, then run a knife along the edges and cool completely.

For the icing, whisk powdered sugar and milk until smooth. Drizzle over the cheesecake before serving.