Display cabinets, until recently, meant deeply untrendy in museological terms. Display cabinets are what museums used to be about when nobody went to them. In today's interactive, hands-on, user-friendly, National Curriculum-geared world they had become a must-not-have, like stuffed animals or propaganda about the British Empire. Some museums today not only do not have display cases, but are not particularly bothered about having a collection of original objects at all. They even try whenever possible to sidestep the fusty connotations of the name "museum" altogether. Witness Eureka in Halifax, Techniquest in Cardiff, or the forthcoming "Explore@Bristol" (the previous working title "Science World" presumably being deemed too dreary by the new museologists and their image consultants). And now here I was in a brand-new gallery full of display cases.

David Bentheim, designer of the "Earth's Treasury", is not only unashamed of the vertical and horizontal cases he has designed for the new exhibition - he even points out to you that some of them are bronze-framed examples recycled from an earlier incarnation of the Museum. Polished up and given a bit of late 1990s stainless-steel trim, in the dim light they pass as new. In fact the whole display, while looking very contemporary, is deeply old-fashioned in concept. Heresy, surely?

Although this is the most extreme example of what might be termed the New Conservatism in museum design, the other three new "earth science" galleries opened last week at the Natural History Museum also have a somewhat retro feel to them. Not so much Victorian retro as mid-1960s retro. I couldn't help feeling, wandering around looking at the big, jazzy colourful images and listening to the slightly condescending soundtracks, that I was elsewhere, back on a school trip to the nuclear-friendly, rocket-science, Dan Dare displays of the old Science Museum. But no - this must have been a subconscious yearning by the designers, some of whom, please note, are working on the displays in the Millennium Dome. The four new exhibitions, added to the existing two completed a couple of years back, complete the £12m transformation of what was once the most overlooked of South Kensington's attractions, the Geological Museum, into the Earth Galleries of the Natural History Museum.