The lack of stone in this lowland region of Tabasco led to the invention of terracotta bricks; mortar was obtained by mixing sand, earth and oyster shells. Comalcalco, near the sea, most likely thrived as a trade centre(600-1000 AD), and architectural similarities with the city of Palenque suggest that relations existed between them: the Palacio, in particular, with its maze of patios and corbeled arches. Don't miss the Tumba de los Nueve Señores (burial chamber decorated with frescoes).