This is the famous Rion - Antirrion Cable Bridge who connect Pelloponisos and Sterea Ellada.

The Rion-Antirion bridge is a cable-stayed bridge near Patra on the Peloponnese, linking the towns of Rion and Antirion on the western mainland Greece, thus connecting with the rest of Europe.

History of Rio Antirio Bridge
The bridge was planned in the mid-1990s. Site preparation and dredging began in July 1998, and construction of the massive supporting pylons in 2000. With these complete in 2003, work began on the traffic decks and supporting cables. On May 21, 2004, the main construction was completed; only equipment (sidewalks, railings, etc.) and waterproofing remained to be installed. The bridge was finally inaugurated on August 7, 2004, a week before the opening of the 2004 Summer Olympics in Athens -- and the Olympic torchbearers were the first to officially cross its length. One of them was Otto Rehhagel, the German football coach who won the Euro 2004 Championships for Greece. Another one was Costas Laliotis, the former Minister of Public Works during whose term the project had begun. The total cost of the bridge was about € 630,000,000, mostly funded by the European Union, and it was finished ahead of its original schedule, which had foreseen completion between September and November 2004, and within budget.

Some technical infos:
Two piers and one beam form the simplest bridge. Such one beam bridge currently achieves a maximum single span of 250 meters.
When necessary, piers and beams are added to form a continuous span viaduct without limited length, the world record being the Lake Ponchartrain causeway in the United States with about 38 km length.
Another traditional technique consists in suspending the bridge to two cables anchored at crossing ends. It results in a supple structure often used to cross deep gorges where no pier can be built.
In the nineteenth century, men had been looking to span longer distances and devised to raise the cables to the top of pylons to form suspension bridges. This technique achieves the longest single span, the world record being the Akashi Kaikyo in Japan with a single span of 1,991 meters