The term 'PLACE FOR A KEYSTONE' can be solved by two crossword solutions: ARCH (4 letters) and ARCHWAY (7 letters). An ARCH is a curved structure that spans an opening, usually made of stone, brick, or concrete. An archway is a passageway with an arched roof or top. Both arches and archways are often used as decorative features in architecture. The keystone is the central stone at the top of an ARCH, which holds the other stones in place. Therefore, an ARCH or archway is a suitable place for a keystone.