Ruby is an ancient town located in the Vallès Occidental in Catalonia. It is located in the valley of the Rubí, and limits the north with Terrasa and San Quirce del Valles, with Ullastrell west, east to Sant Cugat, and south Castellbisbal. With around 73,000 inhabitants, Ruby is the fourth city in population in the Western Vallès, after the two co-capital and Sant Cugat; the twelfth of Barcelona and Catalonia seventeenth. For the rest of Spain falls within the 100 most populous cities in the 97th position.