Pyramid B3 is actually two pyramids built upon a single basal platform. Together they comprise the most important architectural unit in Group B. The northern pyramid of the pair is denominated B3a; the southern is B3b. The two pyramids each have five stepped levels and face west onto the plaza. Each pyramid was accessed by a single stairway flanked by wide balustrades; each had a small altar at the base of its stairway. Both stairways had nineteen steps and the pyramids stand high. Low platforms on their summits indicate where the temple buildings once stood. The double form of the twin pyramids had its origin in the Valley of Mexico and indicates foreign influences at the city. A broken stela was excavated from within the fill of Pyramid B3a; it was a plain monument broken in two parts. The bottom section still stood, while the upper section was lying beside it. It is one of very few such monuments raised in the Maya highlands and such stelae are characteristic of the Classic Period (c. 250–900). It is possible that it stands where originally erected before the pyramid was built over it. A funerary urn was excavated from underneath the rear of Pyramid B3b.