This is known as one of the best aquariums in the world! One can definitely make a day out of it.
Cannery Row is historic in Monterey. You can see how the industry developed and grew in the city, and there are a ton of cute shops to visit.
This is an absolutely stunning preserve, and you can walk through the history of those who made a living off of the sea in its centers.
A beautiful look through Monterey's history as the original state capital, you can visit the Memory Gardens and other historic buildings in this park. Bonus: it's very close to the Barns!