Day trip from/in Dublin

I need to bring a young swedish girl(20) on a short day trip this week by car probably...any suggestions.. Im in dublin so somewhere in the county or at least within the pale...

She is seriously averse to spending any money ( as in a weekend in the country resulted in less than 1 cent being spent) so little point suggesting anything involving her having to pay an admission fee!!!

Walk along Dun Laoghaire pier, sea front in Bray, drive through Dublin/Wicklow mountains, Howth, Malahide Castle. Don't forget picnic

Reckon a visit to Howth is a must its particularly nice especially on a nice summer evening you might even be able to persuade her to buy some Fish n Chips or Malahide/ Portmarnock for a nice stroll on the beach

Botanic Gardens - free and fabulous

I second the botanical gardens. Lived in Dublin all my life, and had never been there until last week. Great day.

We spent our hols in Dublin this year, and made a series of day trips. Got to see things in Dublin that I'd never been to before.

Glendalough with a picnic.