The Cannon Yard (Pushechny Dvor) is the long brick building running along the northern side of the Kremlin courtyard, originally a 17th-century gunpowder factory and arsenal. It is the largest surviving non-religious structure inside the citadel.
After restoration in the 2000s the building became a museum complex containing a small archaeological museum, exhibition spaces, and a permanent display of medieval Tatar weaponry. A pleasant brick-vaulted cafe in the lower level. Worth twenty minutes while you are circulating inside the Kremlin.