is especially true for Mexico City, which offers taco specialties from just about every region of the country. The taco bridges social and economic barriers in that everyone in the country eats them, leading it to be called "the most democratic of Mexican foods." The fillings for tacos vary widely and most taco vendors have a specialty, the most known are al pastor and bistek. There are also tacos for more adventurous people that are filled with beef eyes, brains, or tongue. Taco vendors are usually distinguished from other street food vendors by having a large block of wood called a tronco, on which meat and other fillings are minced with a cleaver. Garnishes vary but usually include chopped onion, cilantro, various salsas, grilled green onions, and lime wedges. Many taco varieties are generally available only in the morning or afternoon. Tacos most often found in the morning hours include tacos de canasta and those with barbacoa or cabeza de res (lit. beef head). Tacos de canasta (basket tacos) are the only kind that are not prepared on the spot. They are tortillas with fillings such as potatoes, chorizo sausage, pork rind, beans and picadillo (a spiced ground meat), then steamed and wrapped to keep warm and carried in a basket. Barbacoa is pit-roasted meat. It is most commonly found in the center of the country, where the preferred meat is mutton. In the north of the country, there is a version made with beef. Cabeza de res are made from meat and other parts of a steer, most commonly found in Sonora, the Bajío region and Mexico City. Vendors of these kinds of tacos usually sell out and close by midday. In the afternoon, outside of Mexico City, tacos are generally not available until later in the day. In the late afternoon until well into the night (especially on weekends) other taco stalls open with a different selection. These are principally grilled, fried, or steamed meat. One famous night taco in the Mexico City area is tacos al pastor (shepherd-style tacos). They are an adaptation of Middle Eastern spit-cooked meat, introduced by Lebanese immigrants. However, the meat is pork and the seasoning is a mild chili pepper, onions and pineapple. Other taco varieties include tacos de guisado, or tacos de cazuela, which are filled with meat or vegetables in a sauce. Fritangas are tacos with fried meat such as