Architect John Messina hosts a walking tour of Barrio Libre, one of the two oldest neighborhoods in Tucson, from 9:15 to 11:30 a.m., Saturday, Oct. 1. The tour begins at the Cushing Street Bar and Restaurant, 198 W. Cushing Street. Free. Ronald Stoltz, of the UA College of Architecture and Landscape Architecture, guides a walking tour of the Underwood Family Sonoran Landscape Laboratory from 3:30 to 5 p.m., Saturday, Oct. 1. The tour begins at the UA CALA Sundt Gallery, 1040 N. Olive Road. Free. A self-guided home tour takes place from 9 a.m. to 4 p.m., Sunday, Oct. 2. $20. Register, get more information and find ticket outlets at aiasouthernarizona.org. The tours are part of Architecture Week, presented by the Southern Arizona Chapter of the American Institute of Architects.