Aguascalientes sits in a high valley in north-central Mexico at about 1,900 meters elevation, which gives it a climate that surprises people who arrive expecting central Mexico heat - mild, sometimes genuinely cool in the evenings, the kind of weather that makes sitting in a plaza with a coffee at 9pm not just possible but specifically pleasant. It's a mid-size Mexican city of about a million people that functions completely without needing to perform itself for outside observers, which is either refreshing or disorietnig depending on what you expected, and usually both on the first day.
The immediate area around the posada is the historic center, which has that partiuclar Mexican colonial character where the 18th century and the 21st century exist in the same block without either one making an issue of it. The Plaza de la Patria is the social center of the city, the actual social center of Aguascalientes I mean, with the Cathedral on one side, the Palacio de Gobierno with its murals on another, and the constant movement of people doing what people do in Mexican plazas, which is everything and nothing at the same time. The Mercado Terán is a short walk and has the kind of food stall situation that tourist markets spend years trying to recreate and can't.
The Museo Nacional de la Muerte deserves its own mention because it's one of the genuinely singualar museums in Mexico and most visitors to Aguascalientes don't know it exists - a serious collection of art and artifacts around Mexican death culture that runs from pre-Hispanic through contemporary, housed in an old university building, and which manages to be both academically rigorous and genuinely affecting in a way that - go on a weekday morning when the building is quiet and the experience settles into you differently than it would in a crowd.
The Festival de San Marcos happens every April and is one of the largest traditional Mexican festivals in the country - the city transforms, the fair grounds activate, the streets fill, and Aguascalientes becomes briefly the center of a particular kind of Mexican festive culture that most foreigners never see because they're in Cancun in April. Staying at a historic center posada during the festival is either the best possible timing or requires booking six months in advance, and both of those things, both of those statements I mean, are equally true simultaneously.