Springtime has finally hit DC. The cherry blossoms have come and gone and now the azaleas are in full swing. It is a good time of year to think about the natural environment and landscaping. The National Building Museum is holding a free event May 15 from 6:30 pm to 8 pm on 20th-century modernist urban landscapes by the likes of Dan Kiley, Lawrence Halprin and Paul Friedberg among others. Landscape architects Elizabeth Meyer of the University of Virginia and Gary Hilderbrand of Reed Hilderbrand will discuss ideas for how to sensitively honor and adapt these landscapes in a conversation moderated by Brad McKee of Landscape Architecture Magazine. The event is free but registration is required.