The Marine Aquarium of Trieste hosts the most common marine species found in the waters of the Gulf of Trieste.

The individual species are housed in about twenty medium-small tanks.
Furthermore, the most representative environments of the north Adriatic have been reconstructed in larger tanks.
Lastly, in the large oceanic tank, species of the open sea are housed along with specimens of larger dimensions.

The most famous guest to have inhabited the tank was undoubtedly Marco, the penguin. A specimen of the South African species Sphenicus demersus, he was brought to Trieste from South Africa by a Lloyds motorboat from Trieste in 1953. Marco lived until 1984 in Trieste, and his fame is due to the fact that he often left the Aquarium to take walks along the city banks, diving in the water from the piers and meekly interacting with the people he met along his way.

Inside the Aquarium, there is also a Vivarium, where there are many species of reptiles and amphibians typical of Friuli Venezia Giulia and neighbouring regions. Apart from the pools that host the individual species, the typical environment of karst ponds has also been recreated. There are also some species coming from distant or exotic places, among which a specimen of albino rock python stands out at 4 metres long, housed in a large newly built terrarium.

Curiosity: the water of the tanks that host the marine species is taken directly from the sea to maintain the content of plankton, minerals and nutrients unchanged. In this way, specimens of marine organisms such as algae, sponges, small crustaceans, etc, often grow in the tanks, which would be very difficult to replicate, but at the Marine Aquarium in Trieste, they grow in an absolutely natural way.

The following museums cannot be visited at the moment, as they are involved in redevelopment, reorganization or relocation interventions:

Marine Aquarium - Molo Pescheria, 2
Morpurgo Museum - Via Imbriani, 5 
Museo di Storia Patria (Homeland History Museum) - Via Imbriani, 5