Imperia offers you a very special offer (get 2 at the price of 1!): Oneglia and Porto Maurizio. Two harbours, two historical centers and two different aspects of the same city.
It is simply brilliant, and due to this region you definitely have to visit it, even for just a weekend or a couple of days.
Visit the old village of Porto Maurizio, then go to the Cathedral of Saint Maurice (San Maurizio in Italian), since it is the largest Ligurian church.