Ixmiquilpan is a small city near Actopan in the Mexican state of Hidalgo, around 3 hours by bus from the northern bus terminal in Mexico City (less than MXN$200).
The city itself has a small historic centre, with a cathedral and a statue of the Goddess Diana, also known as DC's Wonder Woman.
Its main draw is its many water parks with thermal water. I chose té-pathe because it's relatively cheap (MXN$140) whilst still contains many facilities. It was also on the way between the city and Actopan which I thought, mistakenly, would be good for taking the bus home.
In fact, its website says I could be dropped off there and their staff said I could get on the bus from there, but the Ovnibus actually doesn't stop there. I missed the last bus (6pm) because they just wouldn't stop, so I took a bus to Pachuca (which did stop) instead. Alternatively, I could have taken the same bus to Actopan to get the bus back to Mexico City, but I wasn't sure about the schedule from Actopan to Mexico City (it would have been a little quicker, although the route would have been almost the same).