Based on its physical attributes:
* Bowl: A cauldron is a large, deep pot, so a bowl is a direct opposite in size and shape.
* Vase: A vase is typically decorative and holds flowers, contrasting with the cauldron's utility and potential for cooking or brewing.
* Coffer: A coffer is a chest or box for storing valuables, while a cauldron is open and used for preparing things.
Based on its figurative meaning (of a place of intense activity or change):
* Haven: A haven is a safe and peaceful place, the opposite of the chaotic or dangerous connotations of a cauldron.
* Oasis: An oasis is a tranquil place, in contrast to the churning and potentially explosive nature of a cauldron.
* Serenity: This abstract noun represents calmness and peace, contrasting with the turmoil and potential for upheaval associated with a cauldron.
Ultimately, the best antonym for "cauldron" depends on the context in which it's used.