The route
Bath Spa sits on the Great Western main line, the same route that continues on to Bristol and South Wales, and it's served frequently enough through the day that there's rarely a long wait for either the outbound or return leg. At 107 miles and under an hour and a half, it's one of the shortest journeys on this list, and the fastest and typical times barely differ, since almost every departure runs close to the advertised time.
What's actually in Bath
The city's defining feature is the Roman Baths, a 2,000-year-old bathing complex built around a natural hot spring that the Romans developed into one of the most important religious spas in their empire — the original Roman-era stonework and lead-lined pool are still visible below street level, alongside a Georgian-era museum built above them.
Above ground, Bath is almost entirely built from the same honey-coloured local limestone, laid out in the 18th century as one of Britain's most complete examples of Georgian town planning: the Royal Crescent (a sweeping curve of thirty terraced townhouses) and the Circus (a circular street of matching houses) are the two set pieces, and the whole city centre was given UNESCO World Heritage status in 1987 on the strength of that unified Georgian architecture. Bath Abbey, a 15th-century church with elaborate fan vaulting, sits in the middle of it all, and the city's Georgian-era spa culture is also where Jane Austen set parts of two of her novels after living here herself in the early 1800s.
Making the round trip work
Bath Spa station is a short, flat walk from the historic centre — there's no need for a taxi or bus to reach the Roman Baths, the Abbey or the Royal Crescent. Leaving London mid-morning still leaves a full afternoon and early evening in the city before the last convenient return service, which is what makes this the one journey on this list that genuinely doesn't need an overnight stay to feel worthwhile.