Just outside Dublin is Co. Wicklow, which is easily one of the most beautiful places on Earth. You can take day bus trips through Wicklow from Dublin, but I recommend staying in the charming town of Enniskerry instead. That way, you can stay out in the beautiful countryside at a charming B&B to soak up the breathtaking Wicklow Mountains.
While driving through Wicklow, you can see where parts of Braveheart and P.S. I Love You were filmed. Also make sure to stop in Glendalough, which is home to 6th-century monastic ruins.