Its name comes from the arrival of 3 ambassadors sent by the King of Siam on the 29th of June 1686. They crossed the harbour, landed in Lanvéoc and went to the Château of Versailles to meet Louis XIV the Sun-King. At that period Siam Street came down to the banks of River Penfeld and went up towards the Landernau Door.
That Siam Street is famous thanks to Jacques Prévert's song. It was a quite narrow street