In early Gothic churches with six-part rib vaults, the columns in the nave alternated with more massive piers to provide support for the vaults. With the introduction of the four-part rib vault, all of the piers or columns in the nave could have the same design. In the High Gothic period, a new form was introduced, composed of a central core surrounded several attached slender columns, or colonettes, going up to the vaults. These clustered columns were used at Chartres, Amiens, Reims and Bourges, Westminster Abbey and Salisbury Cathedral. Another variation was a quadrilobe column, shaped like a clover, formed of four attached columns. In England, the clustered columns were often ornamented with stone rings, as well as columns with carved leaves.