Welcome to the National Archaeological Museum! It has a very impressive collection, especially if you think that the city of Venice was not founded by the Romans, and that all the exhibits were brought here from other places. Also consider that this is one of the oldest museums in Italy: its origins date back to the donations made in the 1500s by a cardinal and his nephew, the patriarch of the ancient city of Aquileia. The two prelates left the Republic of Venice their libraries and rich collections of ancient marble from Rome, Greece, and the eastern Mediterranean. The collections were first placed in the atrium of the Marciana Library, then with the arrival of other substantial donations it became necessary to find them their own building.
While visiting this museum, bear one important thing in mind: you'll see some sculptures which were "restored" and put back together five centuries ago, during the Renaissance. So this is not just a Classical art museum like many others, but also a tribute to the history of collecting, which takes you back to the earliest days when the habit of collecting antiques began to spread.
The path takes you on a journey that touches all the milestones of ancient art: the archaic and Classical Greek, Roman art, and the first years of Christianity. Its centerpiece is the series of portraits of the Roman emperors, starting with that of Augustus. I'd especially like to point out the portrait of Vitellius, whose overflowing and melancholic fatness was depicted in a very expressive manner.
Finally in the last rooms you can admire the most varying archaeological objects coming from all over the world, including works from Egypt, Mesopotamia, and the Etruscans.
FUN FACT: one of the museum's most valuable pieces is an ivory reliquary from the fifth century called "Samagher's capsella", named after the Croatian location where it was found. If you want to admire it even better up front, you can find a 3D reconstruction of it online that lets you experience the thrill of holding this precious box in your hands!