Britain invented passenger rail — the Stockton and Darlington Railway carried the first paying customers back in 1825 — and nearly two centuries later the network is still one of the best excuses to slow down and look out the window. With more than 2,600 stations linked by roughly 10,000 miles of track, some of the country's finest scenery costs little more than a commuter fare.

Scotland claims the headline acts. The West Highland Line from Glasgow crosses the Glenfinnan Viaduct, the largest concrete rail bridge in Scotland and the one made famous by the Harry Potter films, before threading lochs and mountains toward Fort William, Oban or Mallaig. Regular ScotRail services start at about £22-£26 one-way, while The Jacobite steam train runs the Fort William-Mallaig stretch twice daily from June to late October (£76 standard return). Down south in the Highlands proper, Belmond's Royal Scotsman is the splurge option: five-star cabins, an observation car and private distillery and estate tours, departing Edinburgh Waverley — at a price, from £14,800 for two nights up to £62,400 for a seven-night grand tour. The budget workaround is ScotRail's Kyle Line, often called Europe's most scenic route for a fraction of the cost.

The Far North Line is Britain's most northerly railway, running about 4.5 hours from Inverness to Wick and Thurso via the vast, UNESCO-listed Flow Country peatlands. A return costs around £38, and stops include Forsinard, where an RSPB centre sits inside the station, and the half-timbered halt for seven-century-old Dunrobin Castle. From Scrabster near Thurso, a 90-minute ferry continues to Orkney.

In England, the 24-mile North Yorkshire Moors Railway is a heritage steam line through the national park between Pickering and Whitby, calling at Goathland station — Hogsmeade in the first Harry Potter film. Day Rover fares start at £35 and services run late March to early November. The Settle-Carlisle line, completed in 1876, crosses the 1,300-foot Ribblehead Viaduct through the Yorkshire Dales, with singles from £11 to £56 and six restored station buildings you can sleep in. The Hope Valley Line links Manchester and Sheffield through the Peak District (roughly £12-£30 single), passing Edale, the start of the 268-mile Pennine Way, and England's deepest rail tunnel. The cheapest sea air of all comes on Devon's Riviera Line, where off-peak day returns from Exeter to Paignton start around £12 and the tracks hug the Exe Estuary and sea wall at Dawlish.

Book through operators or search tools like Trainline, and note that heritage lines often need reservations while regular routes sell standard singles and returns. Whether you want a £12 seaside outing or a £60,000 rolling hotel, the window seat is the point.