Estructuras Murcielagos y Pet Nah (or the Murcielagos and Round House Structures) are found together at the northern tip of the site. The Murcielagos was the most important building in the Late Classic period (600-1000 AD) in San Gervasio. The principal center of the site was found here and so was the Overlords house. The Round Houses altar is seen with the Murcielagos in the pictures below, it is round like the principal house.

Pet Nah or the Round House itself is very well preserved. This Post Classic period structure is an unusual building due to its two rounded platforms and its altar.