The Juniata River borders the borough. Piney Creek flows into this river to the west of the borough, and Clover Creek to the east. Across the river is Robeson Extension, usually considered part of Williamsburg, but actually lying in Catharine Township. Street names from the borough extend into the Extension, with the addition of Recreation Drive (borders the ballfields) and Home Street (borders Grace Pointe Community Church, former site of the Blair County Children's Home). The Williamsburg Farm show is held at the complex in Robeson Extension.