EntityQ660994· pop 17· linked from 130 articlesimpossible tridentSign in to saveimpossible object or optical illusionConnectionsInternational Standard Book NumberEntitydigital object identifierEntityillusionEntityQ180686EntityJSTOREntityQWERTYEntityoptical illusionEntityop artEntityMartin GardnerEntitytrompe-l'œilEntityambigramEntityPenrose triangleEntityMathWorldEntityMadEntityPenrose stairsEntityimpossible objectEntityAnalog Science Fiction and FactEntitygravity hillEntityEric W. WeissteinEntityAmes roomEntityCategoriesImpossible objectsOptical illusions