场 grounds itself in earth 土: originally the flat threshing ground where a village beat its grain. Any leveled open space inherited the name — markets, stages, airports, battlefields.
机场 airport, 广场 public square, 市场 market, 操场 schoolyard, 上场 to take the stage or field. 场 is also the measure word for events: 一场雨 a fall of rain, 一场电影 a showing of a film — life counted in venues.
Flattened earth 土 — every FIELD, SQUARE, and VENUE stands on it.
广场舞 'square dancing' — grandmothers dancing en masse in public squares at dusk — is China's biggest fitness movement, complete with turf disputes over the best 场.