There is not a seamless waterfront run from Trieste to Miramare, since there’s about a 3 km gap from the Old Port north along the SS14 that’s industrial and not very pleasant. However, there’s a very enjoyable 4 km seafront promenade from Barcola north to Miramare, with great views of the Gulf of Trieste and an opportunity to do a loop around the park/grounds of the Miramare Castle.
Start in Barcola at the marina just south of Pineta Park. Run north toward Miramare. The first 1 km is through a lovely pinewood park (Pineta di Barcola). Continue along the wide, paved waterfront promenade (combination of sidewalk and separate dedicated path) for another 3 km, passing several beaches. There’s one short but steep climb. Arriving in Miramare on the Viale Miramare, do a loop of the 54-acre grounds of the Miramare Castle — a lovely park with terraced grounds and great views of the harbor. At the south the of the grounds, take the stairs down to the harbor and do a quick little jaunt along the harbor road. Retrace your steps to the start.