I had one of the best Couchsurfing experiences of my life in Leon. I shadowed bariatric surgeries in a teaching hospital almost everyday thanks to the father of my amazing host family who was a bariatric surgeon, and I absolutely loved it. On my other days I strolled through downtown Leon which has some beautiful architecture. Find the exquisite Templo Exporatorio del Sagrado Corazon de Jesus and just spend some time in this incredible church.
Cruise on over to the Museo de Arte e Historia de Guanajuato and find the Metropolitan Cathedral. At the other end of the city is the Arco Triunfal de Leon. Walk to the Plaza Principal and find the Archivo Histórico. Also worth noting is the Fuente de los Leones and the Parroquia del Sagrario. You may also want to check out the Instituto Cultural de Leon.