In July 2008 we took a boat out across the Firth of Forth to Inchcolm, a small island with a mediaeval abbey, a resident colony of seabirds and more history per acre than seems fair.
The abbey is the best preserved monastic ruin in Scotland and you can climb, crawl and duck through most of it. Add the crossing itself, with the bridges of the Forth on the horizon, and it makes a very easy case for a day out of Edinburgh.