Large countryside inn with some mystey

A 3-story inn with some mystery added in:

A laboratory hidden behind a secret door in the attic storage room. (The characters were looking for a treasure hidden there by the innkeeper. The visible lever was a fake and the real lever was hidden under one of the large crates. The chest guarding the lever turned into a mimic.)
The inn is built on the ruins of a prison. (The innkeeper asked the adventurers to get rid of a creature that came in from the nearby sewer system. It turned out that the creature was fairly intelligent and had made a deal with the innkeeper so it could stay in exchange for sharing its knowledge in alchemy.)