The Denver Museum of Nature & Science is one of the city’s most important institutions. It has been around for more than 100 years and has a strong national reputation. It’s also a top local tourist attraction and a destination for groups of schoolchildren—they arrive by the busload, more than 3,000 a day. But in a city with showpiece cultural projects by David Adjaye, Allied Works, and Daniel Libeskind, the Museum of Nature & Science is definitely not an architectural icon. In fact, it’s downright ugly.

Sure, there are some fine neoclassical buildings dating to the early 1900s inside the complex, but they’ve long been surrounded by unattractive pre-cast concrete additions, which give the place all the charm of a suburban office building. Even the lovely 1940 Phipps Auditorium—the only older building that can still be seen from the outside—was long ago converted into an IMAX theater, its front steps replaced by an unsightly glass-and-steel entrance. (Yet another addition, a three-story glass façade on the museum’s west side by Hardy Holzman Pfeiffer Associates, from 2002, was much more successful.)

On Wednesday, about 20 visitors to the American Institute of Architects’ annual conference got a glimpse of the latest attempt to introduce some order into the museum’s architectural hodgepodge. The local AIA chapter organized a hardhat tour of a new addition by Denver’s Klipp Architecture (part of gkkworks), now under construction. The project will add a new group entrance, a state-of-the-art storage and preservation facility, and about 20,000 square feet of exhibition space to the museum. The five-story expansion (two stories below ground, three above) will also hide at least some of the building’s unfortunate concrete shell. The addition will feature beige masonry and Indiana limestone on the exterior, said Klipp’s Tom Otteson, who led the tour along with his colleague Garey Dickinson and the museum’s facility director, Elaine Harkins. A glass entrance used shading louvers that move based on the angle of the sun. (The addition is on track for LEED Platinum certification.) Inside, a large atrium connects visitors with the existing buildings. In fact, they’ll have to walk right past the museum’s original 1908 structure, which sits in the center of the complex like an avocado pit.

Otteson predicts that eventually, all of the museum’s pre-cast exteriors will be covered with new additions. Let’s hope so.