Berlin's Pergamon Museum with its world-famous Greek altar is to celebrate a topping-out ceremony in the spring of 2019 after extensive restoration work.

Project coordinator Frank Roeger told dpa of the date during a site visit earlier this week.

Before then the museum would present a "schedule outlook" for the completion of the first phase of construction, he said.

The museum is being renovated in two phases, the first of which started in 2013.

The Pergamon altar, one of the greatest artefacts of the ancient world and a popular attraction in Berlin's Museum Island cultural district, has not been on display since 2014.

Originally the first phase of the rebuild with the altar hall was due for completion in 2019, but numerous problems pushed that date back in 2016 by four years to 2023.

As an alternative, the museum plans to open a temporary exhibition building on November 17 featuring the display "Masterpieces from the Ancient Metropolis with a 360-degree Panorama."

The museum plans to put on display in this temporary building directly opposite the Museum Island some 80 important works from the Pergamon collection, including the largest piece of the Telephos frieze from the Pergamon altar.

The exhibition, designed by artist Yadegar Asisi, allows visitors to experience Pergamon, the ancient city in Asia Minor, in three-dimensional panoramic form.