A container, in particular a bottle, made of thermoplastic material produced by blow molding or stretch-blow molding of a heated preform, the container designed to contain a liquid being flat and having a substantially domed base with outward-facing cavity defining a substantially planar peripheral annular seat for being set on a support, the base being provided with several grooves radiating from the base center. Each groove in its zone of intersection with the annular seat, has a portion of substantially increased width and the two edges of that portion of the groove are curved with relatively large radii of curvature and with respective concavities facing one another.