Östra Södermanlands Järnväg (ÖSlJ) runs narrow-gauge steam trains between Mariefred, Läggesta and Taxinge. The railway describes the journeys as historical trips on trains about 100 years old. It calls itself Sweden's oldest museum railway, founded in 1959, and says it has operated trains around Mariefred since 1965.

Riding the train is the main activity: passengers travel on the route linking the three named places. The railway's website also covers its rolling stock and the seven 600 mm railways that preceded it in the early 1900s. Its regular service is seasonal. Trains run most weekends from early May to late September, with services on many weekdays during summer. On 6 November, the usual season has ended; the next stated operating window begins in early May. Check the timetable and ticket-price information before planning a trip. The website directs visitors to both. Plan around train departures, since the published activity is train service on the route rather than a year-round museum opening.