Fearless grown-ups hurtle down an extinct volcano in homemade vehicles during the PDX Soapbox Derby. It could be a recipe for disaster, but, instead, it’s a beloved annual event held in Mt. Tabor Park, which offers spectacular views of downtown. Spectators bring their own beer and cheer on the fastest — and kookiest — gravity-powered cars. August 20th, starts at 10 a.m.