1. Preheat the oven to 325°F (163°C) and grease a 9-inch springform pan thoroughly.
2. In a bowl, combine graham cracker crumbs, melted butter, granulated sugar, and cinnamon. Press mixture firmly into the bottom and about an inch up the sides of the pan.
3. Bake the crust for 8-10 minutes until lightly golden, then allow to cool completely.
4. Beat the cream cheese on medium speed until smooth and creamy.
5. Add granulated sugar and beat until fluffy.
6. Mix in sour cream, vanilla extract, and cinnamon.
7. Add eggs one at a time on low speed, mixing until just combined; avoid overmixing to prevent cracks.
8. Pour the cheesecake filling evenly over the cooled crust.
9. In a small bowl, combine melted butter, brown sugar, and cinnamon for the cinnamon swirl.
10. Transfer the cinnamon mixture to a piping or resealable bag and pipe in a spiral pattern over the cheesecake.
11. Use a skewer or knife to gently drag through the swirl to create a marbled effect.
12. Optionally, place the springform pan wrapped in three layers of foil in a larger pan with hot water (water bath) to help moisture and prevent cracking.
13. Bake the cheesecake for 55-65 minutes until the edges are set but the center remains slightly jiggly. Avoid opening the oven during baking.
14. Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour.
15. Remove the cheesecake, run a knife around the edges to loosen, cool to room temperature, then refrigerate for at least 4 hours or overnight (6 hours preferred) to fully set.
16. Before serving, whisk together powdered sugar, milk, and vanilla extract until smooth.
17. Drizzle this vanilla glaze over the top of the chilled cheesecake.
18. Slice with a sharp knife dipped in hot water and wiped dry between cuts for clean, neat slices.