[My directions were a link on the twenj.com website but now that that site no more I thought I would repost them here. Regards, Walter]
This trip requires 1 easy change of trains, from the metro to a commuter train. You can get there and back (R/T) with either 2 Rome Metro/bus tickets (1e each & valid for 75minutes), a 1 Metro/bus Daypass (4e), a 3-day pass (11e) or a Weekly pass (16e).
  So the *exact* same ticket you used to board the metro (or bus) is also valid on the Ferrovia Rome-Lido commuter train to Ostia Antica.
  It took me ~50min from the Termini metro stop to Ostia Antica's train station and then a 10 minute walk to the site.
  Take Metro Line "B" towards "Laurentina" and get off at the "Piramide" stop (4 stops from Termini). It's a small station, the Metro stop is outside and below streetlevel and the Lido trains are unseen but parallel to the metro tracks at street level.   Exit the metro car and turn left and you will see escalator/stairs and a sign "Ferrovia Roma-Lido".
  Top of stairs, turn left (crossing over the metro tracks) and you will see 6 platforms. *All* of these trains go Lido and stop at Ostia Antica but not all are used during the off-peak non-rush hours.  An electronic signboard at the head of the platform will show which train is leaving next and at what time (If they are all blank don't worry, one of them will light-up ~10min before departure.
  Also it will be the only train/platform that the locals are using. {There is a w.c. in the station and on Platform 6. If you have time step *right* outside the station and see the Pyramid of Cestius c.18-12BC and the Ostia Gate & walls AD 271-5 with a small museum or visit the Protestant Cemetery nearby (resting place of Keats & Shelley-well his heart is buried there.
Also the snackbar in front of the station has some cheap decent food}.
  Board the train and to ease your mind look above the door at the train station map. Ostia Antica is the 6th stop and takes ~25min.
At the Ostia Antica stop when you 1st get off the train, just across the tracks will be the small station just to the left is a w.c & water faucet, and ~20M in front of the station is a blue pedestrian overpass that you want to take.
  Exit the platform via the pedestrian tunnel and into the station. Just walk over the highway on that ped walkway and just go *straight*, after a couple of hundred meters or so you cross a 2 lane road and the parking lot for the site is 50m in front of you.
In the parking lot the ticket booth (w.c.) & entrance is 50m to the left.  
 Tickets are 4e and I suggest getting the audio guide (4e with picture ID or possibly CC for security). Also have on hand (the Blue Guide Rome is good) or buy a guidebook/*Map* of the site (available at ticket booth & museum). Don't forget to visit the museum (w.c.) and the very historic Synagogue (alittle off the beaten track) on the site.
*Also* be sure to bring water or even better pack a small picnic lunch and have a quiet picnic it any of the hundreds of secluded out of the way spots. There is also a restaurant at the museum.
  After the audio guide tour is over be certain to visit the western end of the site. You can walk around so alone among the maze-like buildings and paths and make amazing discoveries on your own.
  I like the area in the V section of Decumanus Maximus and Via Della Foce. Look for a 2 storey building that you can climb on top of in this area (good view) but also that particular area has some excellent areas to explore and find mosaics, frescos and some pretty cool rooms.
 One overlooked really cool site is under the Baths of Mithras where the "Mithras and the Bull" statue was found, now in the museum but replaced by a copy. On the main road thru the site (Decumaus Maximus) ~75m west of the Capitolium/Forum area, you come upon a main intersection. There is a road (90deg) to your left & right and the main road goes straight but at a slight left angle, at a 45deg angle to your right there is a road/path, take it. You will see on the right 2 red tile covered protected sites followed by 5 trees in a row, take a right after the 5th tree, you will come upon the Baths on your right (it's the last ruin, 2 columns and a taller lone column with a capital on top. Now see the short (3 sections, 1m high) modern cast iron fence (NW corner of the Baths) below that is the entrance to under the baths and statue. If you walk past the statue there is a maze-like tunnel that takes you under the baths, and you can see how they operated.

Thanks Paradise..You bring back many memories of my youth..I used to spend a lots of time at Ostia( our beach in Rome), before it became a metropoli..

Walter, I never thanked you for your directions which I used last year when I went to OA. They were perfect!! Luckily, I already saved them in a word document so I have them for posterity.
Mara

Hi Walter,

Thank you for the post.

I have added it to "Helpful Information: Italy"

Thanks Walter. It's been several years since we visited Ostia Antica and I must admit we didn't see much of the old city, or see many of the things you mentioned. Would love to return and have saved your post. The next time we visit Rome I will print it and take it with us.

Great directions, but I was wondering if anyone has information on how to get there by boat? I saw it listed somewhere and now have lost it!

To be honest, I am not sure if I am confusing Ostia Antica with Appia Antica, but I know there is a boat that goes up the Tiber for one.

Any help?
thanks
Barbara

Does anyone have info for getting from Ostia Antica to the airport?

FCO or Ciampino?

Directions from Ostia to FCO - are there buses or shuttles?

Thank you,