PARIS (AP) — With sunset and moonlight gleaming on the river, the grandiose opening ceremony for the Paris Olympics will last nearly four hours.

A total of 205 delegations will parade on more than 80 boats on the Seine. The ceremony will drift slowly from east to west, bridge to bridge, snaking six kilometers (3.7 miles) from Pont d’Austerlitz to Pont d’Iéna.

Proceedings begin at 3:45 p.m. and finish at 11:15 p.m. local time with artistic performances preceding the athletes’ parade.

The athletes will motor past about 320,000 fans wedged in behind security cordons on upper and lower tiers on the embankments. Others will gaze at giant screens beaming images of the ambitious ceremony.

“For one evening, the Seine will be transformed into a giant open-air ceremony,” Paris Games director of ceremonies Marie-Catherine Ettori said during a media briefing on Thursday.