The Tsakona bridge is a two-span (90m and 300m) steel arch structure, which will be part of the National highway connecting Tripolis and Kalamata, in southern Greece. It is planned to pass over and therefore avoid a large landslide, which in 2003 disrupted completely the traffic in the highway. The paper briefly describes the geological and hydro-geological conditions of the area, as well as the triggering instability mechanism of the landslide. Design criteria for the adoption of such a unique bridging solution are reviewed and the approach followed for the foundation design of the bridge, covering both the selection of appropriate locations and suitable types, is presented. Design and construction processes are described with particular reference on the foundation of the middle pier, which consists of a system of four caissons connected with a large and very thick raft. The detailed geological-mapping that was carried out during construction is also presented which verified fundamental design assumptions regarding ground conditions and geotechnical parameters.