4 days in Ireland for five 22 year olds, Suggestions?

I think Belfast would be interesting. By train it doesn't take long.

Is that 4 full days, or are you including your travel days in and out of Ireland on the front and back end and you really only have 2 full days? Your answer to that would influence my response (and likely others). If you have just 2 full days, I'd suggest base yourself in Dublin the entire time and take a couple day trips nearby. If you have 4 full days, then train to Galway and you can base yourself there for a night or two and do some day trips (a lot of day tour operators will have various trips from Galway to places like Cliffs of Moher, the Burren, Aran Islands, etc.). Other option would be train to Belfast and see the city and some of Northern Ireland (Antrim Coast, Giant's Causeway).

You aren't going to be able to rent a car if everyone is 22. You'll need to stick to trains (service is relatively limited) or the buses (which pretty much go everywhere). But you really need a minimum of at least 2 days to see Dublin, so you are a bit limited as to how many other places in Ireland you can cram into that short a time frame.

Thanks for the quick response! We will be there for 4 full days.

I visited Ireland for the first time when I was 27. I've been back four times. Here are some suggestions:

1. Pub crawl: The Literary Pub Crawl in Dublin might be fun: http://www.dublinpubcrawl.com/. I've been on it twice.

2. Hurling: On a visit in 1999, I stayed in a bed & breakfast across the street from Croke Park, Dublin's biggest athletic venue. It seats around 70,000 fans. I'm still kicking myself for not going to a hurling match. I didn't go because I had jet lag and was sleepy. It looked like fun event.

3. 1916 Uprising Centenary: You're visiting exactly 100 years after the 1916 Uprising. The country has a whole bunch of commemorations planned. Go here (http://www.irishtimes.com/culture/heritage/easter-rising-commemorations-50-events-for-2016-1.2492549), here (http://www.taoiseach.gov.ie/eng/Historical_Information/1916_Commemorations/) and here (http://www.visitdublin.com/see-do/details/easter-rising-centenary/510660/#53.349805|-6.260310|16) for information.

4. Kilmainham Goal: One of the most interesting sties I went to is Kilmainham Gaol (jail). You learn a lot of the Irish nationalism and the rebellion against the British.

5. Museums: My favorites include the Dublin Writers Museum, the Book of Kells exhibit at Trinity College and the National Gallery. Google them. There are dozens more museums. Get a good guide book on Ireland, and they'll all be listed.

6. Brewery/Distillery Tours: The Guinness Brewery tour and Old Jameson Distillery Tour are aimed at tourists but fun anyway. I've only gone on the Jameson event.

7. Outside Dublin: There are two sites nearby that are worth seeing on a short trip. Go to the tourist information office in Dublin to inquire about day trips or buy a good guide book to look these up. Glendalough is a Christian monastic site that's more than 1,000 years old. It's a stunning site and the Wicklow Hills are beautiful. Go here: http://www.glendalough.ie/. Also the Rock of Cashel is a stunning medieval site. It's a bit farther afield from Dublin but worth it: http://www.cashel.ie/.

There's plenty to keep you occupied in and around Dublin, with maybe a day trip by local train to Howth on the coast, a cool beach town with good pubs. Also Glendalough as mentioned previously.

If you want to experience a different part of Ireland I agree with Ceidleh, either Galway on the west coast or Belfast in NI are good choices, each of them about 2-1/2 hrs by train. I loved both of them. Galway is much different than Dublin, smaller, more intimate and in the gaeltacht region (where many speak the old Irish language), lots of traditional music pubs and busy pedestrian only area. It was one of my favorite stops in Ireland. Belfast was tremendously interesting because of all the history in recent memory (well not recent memory for some 22 yr olds, but recent to me. lol). Fascinating sights to visit including the shipyard where the Titanic was built and the museum there and also the many murals on the buildings depicting the 'troubles'. Either one would be a good choice.

To do day trips to Cliffs of Moher, the Burren, and others in that area, is it better to have Limerick or Galway as a base for a night based on the two cities? Is Limerick similar to Dublin?

Nothing inherently wrong with Limerick but Galway has much more character. Probably equally easy to do day trips to the cliffs and burren from either but I highly recommend Galway. I doubt if many here would recommend Limerick. It's not the prettiest town in Ireland, maybe a bit gritty.

To do day trips to Cliffs of Moher, the Burren, and others in that area, is it better to have Limerick or Galway as a base for a night based on the two cities? Is Limerick similar to Dublin?

Galway. For one Galway is closer to the Cliffs and the Burren. Galway is much more appealing city than Limerick, too. Galway also has great bars and sites.

Limerick is a bit of a dump. Galway is much more lively and, with the university there, has a good sized population of students living in the area that are about your age and will make your pub crawls a lot more fun. I don't think I noticed what month, exactly, you are planning this trip. You should note that festival season is going to start to gear up in and around Galway as the weather starts to warm up and reaches its peak in the summer and early autumn. The Fringe Festival, Galway Arts Festival and Galway Races are some events that draw huge crowds in the city with parades, performances and lots of people packing the streets, pubs and nightclubs. Check the calendar of events at galwaytourism.ie to see what's happening in the city during your visit as you may need to book lodging ahead of time during some of the bigger events (especially if you are in need of more budget accommodations or landing enough bunks in one of the local hostels).