I found the Maritime Museum very interesting.

The Maritime Museum of Barcelona
The centerpiece of the museum is a huge replica of a medieval ship. You may walk around it or go up on board and look inside.

The Maritime Museum exhibit
The ship looks very nice, interesting and rich.

Replica of a medieval ship
Apart from the ship you can see numerous models of other sailing devices from the first floats to modern ships. There are also a lot of pictures and historic documents there. To spend a couple of hours in the museum will certainly be interesting both for children and adults.

Ancient sailing devices
After visiting the museum we went to the square called Portal de la Pau.