Real de Catorce is a spanish colonial town, translated as "Royal Fourteen". it is accessable by a dual sport or 4 wheel drive only road up a valley, or on the official highway, a 10+ mile long hand laid 3 lane cobblestone road older than the US. At the end of a highway is a tunnel, about 1/2 mile long, with walkie talkie traffic control and a nominal toll. Exiting the tunnel into Real is a time warp.
If you've seen "The Mexican" with brad Pitt and Julia Roberts, a lot of the movie was filmed in and around "real". If you haven't seen the film, it is actually really really good, for Brad Pitt movie. Brad exiting the tunnel.
Hotels are $40 tops ( I stayed at the one in the movie...before the movie), a bed in a smaller hotel $8. Donkey rides $10 to the high mountains and plentiful Pejote plants and guided "trips", lol.