Orsedd Bridge is an area in Breath of the Wild.
Breath of the Wild
The Orsedd Bridge is located just east of the Hyrule Castle Town Ruins. It follows along the main path, passing from the Romani Plains over the Hylia River and through the Crenel Hills. The water underneath the bridge flows fairly rapidly with some Hyrule Bass and Staminoka Bass swimming in the area.
At the west side there is an acorn hanging down from the bridge. Shoot it with an Arrow to get a Korok Seed. Underneath the bridge, Link can find an enemy Water Octorok that will attack Link when he's nearby.
In the water under the bridge to the east, there is a treasure chest that contains an Opal gem. A second treasure chest can be found to the northwest of the bridge and it contains a Soldier's Claymore. Another treasure chest can be found in the water much further northwest, between the Orsedd Bridge and the Boneyard Bridge, and this one contains a Purple Rupee.
Nearby Korok Seeds
There are three balloons in total that you need to shoot once you touch the small pinwheel. The third one is hiding in the log.
Destroy the acorn.