Towne Lake resident Eric Siegel hosts the annual event, featuring his large O-Scale model railroad layout, 10 a.m.-6 p.m. at 640 Overhill Drive in Deer Run. The Appalachian and Western Railroad is a 900-square-foot display that fills his basement. The layout is still under construction, so anyone interested in getting into model railroading can see how it’s done. The open house is part of a larger tour of Atlanta area model railroads called the Piedmont Pilgrimage. www.piedmontpilgrimage.com. Complimentary snacks and beverages will be available. For details, call 404-400-2993. Admission is free; no reservations needed.