The number of people standing in line this week was unprecedented as London got its second major public exhibition opening of the year. After the reconfiguration of the Tate Modern, we have a new Design Museum.The Switch House and Tanks almost doubled the size of the Tate Modern located on the South Bank. In this latest separate development, the Design Museum has made an even more dramatic move, tripling its size to 10,000 square meters. It has moved from south of the Thames to South Kensington after a £85 million ($106 million) refurbishment of the former Commonwealth Institute. So we have a new museum of sorts, not quite a new building – though an exceptional piece of architecture with claims to being one of London’s best of its kind.The curiosity among visitors and demand of tickets may have taken some by surprise, but the museum staff members were being unfailingly helpful in response to the crowds. The exhibitions were packed, making it hard to get around some comfortably, though this will doubtless become easier as numbers drop to more manageable levels. The museum is more accessible than its former location, so its footfall will surely increase. There are estimates of 650,000 visitors in its first year.A report from the frontline of the opening today showed the museum still settling in, with some landscaping still to be finished, the Parabola Restaurant rapidly booking out and not all washrooms finished and open for use – though they are of course impeccably designed, with self-dispensing soap, water and drying facilities built in to the mirrors. Surely the teething problems will soon be fixed and the museum is on its way to becoming a major attraction for students and anyone interested in design – from kettles to cars, or chairs to shopping centers.The Design Museum is now effectively in its third location: long-term followers will remember it was started in 1983 by Sir Terence Conran in the basement of the Victoria & Albert Museum under the name the Boilerhouse Project. (Those of us who still have its original paperback beige-covered guide can only marvel at its elaborate typography on the cover.) The V&A kept its fashion remit and the Conran design project rapidly needed space for its growing scope and ambitions under Stephen Bayley. The concept, formally becoming the Design Museum in 1989, moved from the V&A to a former banana-ripening warehouse in Shad Thames, south east London. This was also the home of the impressive Blueprint Café, originally by Conran, later taken over by D&D London, and known for its seafood. In the heyday of yuppies, one recalls it was one of those great pre-millennial places for summer sunset cocktails.Those with longer memories will also recall visits to the Commonwealth Institute, as it was. We would enter via a covered walkway to emerge in the middle of the square building – which, if it were for sale, real-estate agents would doubtless describe as “stunning,” and with justification. (The present writer first visited about 1974.)It is hard to overpraise original architects Sir Robert Matthew and Johnson-Marshall & Partners. The 1962 building was frankly astonishing and perfectly suited for its display of Commonwealth country culture. The square foundation base was capped with a pavilion-style roof which had echoes across 1960s architecture, before and after its construction, from the small (the Evans House in Connecticut) to the larger (the Church Army Chapel in Blackheath, London, to name but two).Inside, the central and lower floors had large celebratory and educational displays for major countries such as Australia and Canada. Visitors could gradually ascend toward the hyperbolic parabola roof, and some of the most amazing vistas were on the tiny balconies with the small island nations such as Tonga at the top – with breathtaking views on to top floor over the whole displays. The charity that ran the worthy venture had its fate sealed as the concrete roof started to leak and the whole thing acquired Grade II listed status, making it all but impossible to restore economically. The structure was left vacant in 2002 in a sad state of repair; this writer revisited it shortly before closure and found it a very sad shadow of its 1970s heyday. Architectural historians will hopefully celebrate its retention in whatever form. The current Design Museum director Deyan Sudjic has been seeking new premises for a decade, with the current scheme in progress since 2008.While some people regarded the old institute as hosting a construction of modernist brutalism, others saw it as one of the most extraordinary edifices in London, even with a pedestrian administration block adjoining it, now thankfully demolished. The main structure is now partly screened from Kensington High Street by Holland Green, boxy residential blocks by Allies and Morrison – helping fund the project (£4.6 million came from the Heritage Lottery Fund and the Arts Council and much from Conran himself) though shutting off some spectacular sight lines. The former institute’s row of proud national flagpoles is reduced to a symbolic showing. At least, the building’s soaring roof can be appreciated from the northern parkland; and visitors enjoying a Bloody Mary in the new restaurant bar currently have a stunning view over Holland Park’s autumnal leaves.OMA, Allies and Morrison and Arup have restored the spectacular concrete roof. The distinctive façade has double-glazed windows that match the original blue skin and let in more light, which is a vast improvement. The original stained glass “Commonwealth” windows by Keith New remain, filling the ground floor shop with color.The original concrete floors were stripped out with the roof temporarily floated on a steel scaffold during the rebuild process.Architect and designer John Pawson’s sensitive and thoughtful refurbishment with an oak-lined interior faced the enormous challenge of how to keep the roof sight lines. The result partially works in the atrium on arrival in the building, though arguably something of the vast cathedral-like space has been sacrificed for more exhibition areas.While there are a lot of design institutes and museums worldwide, the London one has the ambition, according to the news release, of being “the world’s leading institution dedicated to contemporary design and architecture.” Apart from the building’s considerable design merits, the case is also put strongly by some of the exhibits. The museum has previously feted Lord Rogers, Thomas Heatherwick, Dame Zaha Hadid, Sir Paul Smith, and Sir Kenneth Grange. The current exhibits (frankly infinitely more exciting than those in the building’s previous incarnation) say a lot about British design: the Mini car, stylized Underground maps, the Anglepoise adjustable desk light, Penguin book covers, Sir Giles Gilbert Scott’s telephone kiosk and much more. There are interactive displays, videos and plenty to admire.The museum’s permanent collection, “Designer User Maker,” on the top floor is free. The other temporary exhibitions on the lower floors are ticketed, such as “Beazley Designs of the Year,” showing award-winning contemporary design (November 24 through February 19) and “Fear and Love: Reactions to a Complex World,” showing major commissions (November 24 through April 23).The Design Museum, 224-238 Kensington High Street London, W8 6AG. Information: https://designmuseum.org/   Read more