You see a sturdy chest.
Notes
When you try to open it with the correct item and fail, you will see: "CRONK!" and it will produce a yellow spark effect. If you succeed, you will see: "CLICK!" and it will produce a gray spark effect.
It looks the same as a Chest, a Chest (Quest), a Storage Chest, and Iriana's Chest.
Part of The Thieves Guild Quest, you need to use Lock Picks on it to get a Valuable Vase.