South Queensferry sits about 10 miles west of Edinburgh, directly beneath the three bridges that cross the Firth of Forth here: the red cantilevered Forth Bridge from 1890, the Forth Road Bridge from 1964, and the Queensferry Crossing from 2017. It's a proper harbour town rather than a viewing platform for the bridges, with a cobbled High Street, a working pier, and a history that goes back centuries before any of them were built. If you've already covered the things to do in Edinburgh hub and want somewhere genuinely different for a few hours, or you're weighing it against the rest of my day trips from Edinburgh, this is the case for it.
The town takes its name from the ferry crossing itself: Queen (later Saint) Margaret used it to cross the Forth in the 11th century, and a passenger ferry ran here for the best part of 900 years until the Forth Road Bridge made it redundant in 1964. That layered history is still legible if you know where to look: the harbour and Hawes Pier the ferries used, the Hawes Inn where travellers waited for the crossing (and where Robert Louis Stevenson is said to have set a scene of Kidnapped), and now three bridges from three different centuries, all visible from the same stretch of shore.
The honest shape of a visit is this: a half day covers the High Street, the bridges and a pub lunch comfortably. Give it a full day if you're adding the boat trip out to Inchcolm Abbey, which alone runs close to three hours there and back. Here are the twelve stops I'd build it around, roughly in the order I'd visit them coming off the train or bus.