See the 170 metre Spinnaker Tower near the sea. The sail-shaped building is impossible to not miss!
A curious historian? Take a visit to the Mary Rose Museum. There lays the 512 year old Tudor ship as preserved as one can be.
While your're around the Portsmouth Historic Dockyard, perhaps take a look at the HMS Warrior. Build between 1859 and 1861, the ship was used by the Royal Navy and stayed in used until 1987.