Around 2km south of San Ángel, Insurgentes enters the great lava field of El Pedregal, which gets its name from the vast lava flow that spreads south of San Ángel through the University City and beyond. Craggy and dramatic, it was regarded as a completely useless stretch of land, the haunt of bandits and brigands, until the early 1950s, when architect Luis Barragán began to build extraordinarily imaginative houses here, using the uneven lava as a feature. Now it’s filled with an amazing collection of luxury homes, though you’ll unfortunately be able to see little of what is behind the high walls and security fences even if you drive around. El Pedregal is also home to the university campus, the Olympic Stadium (Estadio Olímpico) and Cuicuilco, the oldest pyramid in central Mexico.
The Pirámide de Cuicuilco is dominated by the circular temple visible to the east of Insurgentes by the periférico, around 3km south of the Estadio Olímpico and opposite the former Olympic Village, now a housing complex. This is much the oldest construction of such scale known in central Mexico, reaching its peak around 600–200 BC before being abandoned at the time of the eruption of Xitle (the small volcano that created El Pedregal, which took place around 100–300 AD), just as Teotihuacán was beginning to develop. Not a great deal is known about the site, much of which has been buried by modern housing (completing the work of the lava). The pyramid itself, approached by a ramp and a stairway, is about 25m high by 100m in diameter and is composed of four sloping tiers (of a probable original five), the lowest one made visible only by digging away 4m of lava. A small museum displays objects found here and at contemporary settlements.