The National Aquarium in Baltimore is celebrating its 33rd anniversary.
The aquarium opened on Aug. 8, 1981, and became the centerpiece of the city's revitalized Inner Harbor.
On Friday, the first 500 visitors will receive a free slice of cake to mark the occasion.
The aquarium is also marking the first anniversary of its Blacktip Reef exhibit. The 270,000-gallon exhibit is a replica of an endangered Indo-Pacific coral ecosystem. It's home to 70 different species, including blacktip reef sharks.