Honestly, the easiest way to get there is to book a tour. Seriously. They pick you up, they drop you off, you don’t have to figure out the bus schedule—it’s a whole thing somebody else handles. This is the list of options:
By Train
Head to Trieste Centrale. Grab a regional train—if the schedule feels like cooperating—and it’s maybe 9 minutes to Miramare station. Once you’re off, there’s a walk down via Beirut, through the park. Not far, 150 meters or so. The tickets are cheap, just a couple of euros. A pretty reliable option.
By Bus
This gets complicated.
You can take the 6 or the 36. The 36 goes right there, get off at the last stop. With the 6, you get off at Grignano and walk, maybe 700 meters from the stop to the park entrance. In summer, just know that both lines will be absolutely packed with people. A mess.
Now, tickets. You can get a single hourly ticket, the “biglietto orario,” which is fine for one trip. I think it lasts longer on Sundays, but who knows if that’s still true. If you’re planning more than two trips, it’s probably better to get the daily ticket—“giornaliero.” And there’s a 10-trip multi-ticket you can buy from blue totems at some stops. The “biglietto giornaliero regionale” should be valid for any of the urban lines. Anyway, it’s a lot to figure out for a bus ride that costs less than €2.
On Foot
If you start from the Barcola area on the coast, you could walk it. But it’s a real walk, maybe 6 or 7 kilometers depending on your starting point. Don’t try it without water. The coast is nice, but it gets long. Really long.
By Car or Taxi
Someone mentioned this is the best way since the castle is pretty far from the city center. It’s about a 10–15 minute drive, something like 8 or 9 km from central Trieste. There’s parking near the castle, but it fills up fast, especially on nice weekends. A taxi, of course, skips all that.
By Boat
There’s a ferry. It’s a summer-only deal, and I saw something about it running until October 11th, though that date might be old. It leaves from the port downtown and goes to the bay at Grignano. It costs more than the bus and takes longer—maybe 50 minutes—but the views are obviously better if you’re willing to pay for the privilege.
What Actually Works?
The train is probably your best bet. It’s fast. Go mid-morning to avoid the worst of the crowds. I’d even say see the park first; it frames the castle better when you first see it from the outside.
Then you could take the bus back for a different view. Or walk part of it along the coast if you have the energy. I still haven’t figured out the perfect route.
Things to Know
Check the schedules before you go. This sounds obvious, but off-season they can be weird. If it’s hot, the train is infinitely better than waiting for a bus that might be full. And wear good shoes for the park. There are steps and the ground isn’t perfectly even. For some reason, that always gets me—the paths look flat but they’re not.