Time Out says
Sloppy passata, proper mozzarella and a light, fluffy crust blistered by the wood oven, O'Hara's are sterling pizzas. Situated on the riva, with several boats moored on the other side of the road, grab a seat on the outdoor terrace. Booking in advance is advised to ensure a spot as O'Hara is justly popular. Busy over summer weekends in the weekday evenings, O'Hara Rijeka is equally popular in winter when the action moves indoors, the terrace last year being reserved for the alfresco cooking of mulled wine and sausages. If you're a fan or (ambitiously) aiming to eat only one pizza in Rijeka, O'Hara should be first on your list.