My senior colleague (she'll start the three-year phased retirement process next year) took her students in the Nuclear & Particle Physics course and had them write things (and explain what they were writing) with sidewalk chalk out on the Quad (cement pavement). The Meson nonet, proton structure, Feyman diagrams for weak and electromagnetic interactions, and so on. Unfortunately it happened the weekend after (not before) the annual rock concert on the Quad.
Probably just about all gone by now, since it started drizzling since I got in an hour and a half ago. Pity.