Serota, praised the donation saying it would help to make Tate Modern a "truly twenty-first-century museum". The Tanks The first phase of the expansion involved the conversion of three large, circular, underground oil tanks originally used by the power station into accessible display spaces and facilities areas. These opened on 18 July 2012 and closed on 28 October 2012 as work on the tower building continued directly above. They reopened following the completion of the Switch House extension in June 2016. Two of the Tanks are used to show live performance art and installations while the third provides utility space. Tate describes them as "the world's first museum galleries permanently dedicated to live art". The Switch House A ten-storey tower, high from ground level, was built above the oil tanks. The original western half of the Switch House was demolished to make room for the tower and then rebuilt around it with large gallery spaces and access routes between the main building and the new tower on level 1 (ground level) and level 4. The new galleries on level 4 have natural top lighting. A bridge built across the turbine hall on level 4 provides an upper access route. The new building opened to the public on 17 June 2016. The design, again by Herzog & de Meuron, has been controversial. It was originally designed with a glass stepped pyramid, but this was amended to incorporate a sloping façade in brick latticework (to match the original power-station building) despite planning consent to the original design having been previously granted by the supervising authority. The extension provides of additional gross internal area for display and exhibition spaces, performance spaces, education facilities, offices, catering and retail facilities as well as a car parking and a new external public space. In May 2017, the Switch House was formally renamed the Blavatnik Building, after Anglo-Ukrainian billionaire Sir Leonard Blavatnik, who contributed a "substantial" amount of the £260m cost of the extension. Sir Nicholas Serota commented, "Len Blavatnik's enthusiastic support ensured the successful realisation of the project and I am delighted that the new building now bears his name". Galleries The collections in Tate Modern consist of works of international modern and contemporary art dating from 1900 until today. Levels 2, 3 and 4 contain gallery space. Each of those floors is split into a large east and west wing with at least 11 rooms