Ballcourt B1 is immediately south of the Group B plaza, with the northern entrance to the ballcourt directly accessing the plaza itself. It is an enclosed sunken ballcourt, as was common in the Maya highlands during the Late Postclassic. The ballcourt is aligned north-south with two transverse end zones forming a capital I shape. The ballcourt has two entrances in the form of inset stairways in the end zones, in the centre of the ballcourt's north and south walls. The side walls of the playing alley are slightly sloped and are topped by a cornice; the playing alley is flanked by two low benches set against the east and west walls. The end zones also possess sloping walls. All the ballcourt walls were built of large stones. The ballcourt playing area measures north-south and is wide between the benches. The end zones measure east-west. The ballcourt was originally coated in stucco painted in a variety of colours; very little of this coating now remains. A drain opening empties runoff rainwater from the east side of the northern end zone; the drain continues under Platform B 2 and empties outside the retaining wall of Group B.