Berlin, July 10 -- Berlin is opening a new addition to its Museum Island complex, a stylish building described by officials as a milestone in a long-term effort to renovate the neoclassical ensemble that is home to treasures such as Babylon's Ishtar Gate and a famous bust of Egyptian Queen Nefertiti.

Designed by British architect David Chipperfield, the James Simon Gallery was presented to reporters Wednesday and opens to the public Saturday. Built on a narrow riverside site with a colonnade stretching along the bank, it provides an imposing entrance to the UNESCO world heritage site.

The building includes exhibition space but is meant largely to make the museums more user-friendly, providing facilities such as a cafe, shop and auditori...