Sjundby Manor is one of Siuntio's great historic houses, with a stone main building dating from the 16th century and a history tied to noble families, Swedish rule, and the Porkkala lease after the Second World War. It is still privately owned, so access depends on guided tours and events.
Even with limited access, Sjundby gives the municipality its strongest sense of age. If a tour is available, take it; otherwise the setting still helps explain why Siuntio is more interesting than it first appears on the map.