Ronneburg is a small municipality in the Main-Kinzig district of Hesse, about 35 km east of Frankfurt, formed in 1972 from the villages of Altwiedermus, Hüttengesäß and Neuwiedermuß and named after the castle that stands on a basalt spur above Altwiedermus, between the Wetterau plain and the Vogelsberg hills. Burg Ronneburg is a 13th-century hilltop castle that has kept its medieval layout unusually intact: a ring of walls and towers around an inner courtyard, a keep, a Gothic hall, the medieval castle kitchen and one of the deepest castle wells in Germany.
It was a residence of the Counts of Ysenburg-Ronneburg and, in the 18th century, a refuge for religious dissenters — the Moravian community of Count Zinzendorf lived here in the 1730s — before serving as housing for displaced families after 1945. The castle is run by the association Freunde der Ronneburg e.V., open from March to November (Tuesday to Sunday, 11:00–17:00) with an armoury, a furniture collection, falconry displays and a calendar of medieval markets, and it reopens for the historical Christmas market on the first three Advent weekends. The nearest medieval town is Büdingen, about 8 km to the north-east, with its complete ring wall and gates.