My husband and I are flying to Venice this weekend and have a 9.5 hour layover in Dublin.
We spent 12 days in Ireland last year and loved it.
We want to go into the city for 7 ish hours and explore.

I have a couple questions...
What is the best way to get transportation to the city centre? Also, what is most recommended to do in a short time frame?

We have already done the Guinness tour, the and Kilmainham Gaol. We only spent one night in Dublin during our last trip. We missed the book of tells, temple bar area, and trinity college last time we were in. Are those must do items or is there something better to do?

Thank you!

I would probably go to Malihide castle, walk around the town, have a meal and then head back to the airport. Cab would work for all of that. We take the 747 bus into town from airport. I would go eat at one of my fav places, pop into a few stores and stroll around St Stephens green. Howth would also be a good option.

Macross - how far is that castle from the airport? I haven’t heard of it before but it looks cool! We enjoyed exploring castles when we spent time in Ireland.
How far is the castle from like temple bar area?

8.5 km airport to castle, the village is also very nice. 17 km to Howth from Dublin airport. It is about 45 min from Airport to Temple bar because of stops and traffic.

Stop all the horses and all the traffic. There are 2 absolute must sees that you've missed in Dublin. I'd take a taxi from the airport (fastest way) and do one of these:

National Museum of Ireland- Archaeology (closed Mondays. Address: Kildare Street, Dublin 2). - Did I mention this is an absolute must see? Probably will need at least 3 hours here. See all the Ireland exhibits first.

Book of Kells- also, absolute must see. Great exhibit there to read through before you see the actual Book of Kells. This exhibit is in Trinity College, so can also do the tour of trinity college when you're here, it's an interesting tour given by students.

I agree with Beatlemania's recommedations and would add high tea at the Lord Mayor's Lounge at the Shelbourne Hotel. It's a grand spread with a friendly atmosphere. Check the times on their website. And depending on you time and energy a walk through St. Stephens Green.