aquarium — An aquarium is a building, often in a zoo, where fish and underwater animals are kept.
herbarium — a collection of dried plants systematically arranged.
Four-or-more syllable rhymes
honorarium — a payment in recognition of acts or professional services for which custom or propriety forbids a price to be set: The mayor was given a modest honorarium for delivering a speech to our club.
planetarium — an apparatus or model representing the planetary system.
