I visited this WHS in December 2021 (the aqueduct proper) and in January 2022 (Otumba and Zempoala). After a magical hot air balloon ride experience over Teotihuacan, I drove for a few kilometres on the highway to the Father Tembleque Aqueduct.

Coming from Teotihuacan it's a very easy drive and the best panoramic views are indeed from the highway. However, just when you get to about 500 metres from the aqueduct, suddenly there is no paved road, so you either park in a quiet side street or do some offroading while paying attention not damage the car if you don't have much clearance. I opted for the latter as we had our valuables in the car and slowly but surely we made it to the aqueduct. As others have said, the aqueduct is a fine construction and was vital for the local populations at the time, but it is less impressive than others in Mexico such as in Morelia, Zacatecas or Queretaro and especially others in Europe (Segovia, Pont du Gard, Evora, Pontcysyllte, etc.). It isn't large either, so I made an extra effort to walk from one end to the other, crossing the Papalote River and enjoying the ancient volcano landscape. Half way through there are also railway tracks underneath the aqueduct. Along the aqueduct there are three arcades: the first with 46 arches, the second with 13 arches, and the third with 67 arches, with the tallest arch being slightly less than 39 metres high.

In Zempoala, the aqueduct canals split into two 16th century square cisterns which provided water to the key complexes in Zempoala, such as the Main House or the seeming out of place and huge Todos los Santos Ex Convent. Next to one of the sides of the former convent, behind the convent wall in the main road, there's also a very small garden dedicated to Father Tembleque and the aqueduct. Having visited both Zempoala and Otumba, I would argue that the water cistern here together with the ex convent, are more accessible and offer more than Otumba's minor sites. So if you don't care about UNESCO WHS plaques and you only have time for one of these towns (without missing the aqueduct proper), I'd recommend choosing Zempoala over Otumba.

In Otumba, there are replicas of the aqueduct in every other roundabout or square. There's a statue of Father Tembleque in front of the big Convent of La Purissima Concepcion and the rear side of the convent's perimeter is an overgrown empty water reservoir with modern glass walls separating it from modern-day traffic, a UNESCO WHS plaque facing the busy side street and a small painted description on one of the stone walls of why the aqueduct hydraulic system has been inscribed on the WH list. Further on, towards the town's dirty and almost abandoned outskirts lies a small water tank, now occupied by stray dogs as their kennel. Not seeing any dogs upon my arrival, I ventured inside the water tank (nothing worth writing home about) and apart from a foul smell, I also risked being attacked by stray dogs resting inside: one was "on guard" and the other was laying on the ground feeding cute baby puppies. In Zempoala and on the way to Otumba, I had already noticed other similar water tanks but without the stone cross on top.

In the central section of the aqueduct's underground canal system, a number of haciendas are connected to the water canal before the hydraulic system enters the municipality of Otumba, such as the Hacienda of Santa Inés and the Haciendas of San Miguel Ometusco and Zoapayuca in the municipality of Axapusco. The town of Otumba marks the southern end of the hydraulic system, once more integrating several diverter tanks and water storage tanks. Their provision can still be understood in some architectural structures, such as the House of Culture, the House of Viceroys or
the Convent of La Purissima Concepcion. Having seen more than enough, I decided to skip the "tour" inside the Gonzalo Carrasco regional museum and drove back to Mexico City.

Not only is it surprising that the Father Tembleque Aqueduct made it on the WH list, but it also got inscribed under three criteria! So, mostly because there was no UNESCO WHS plaque near the aqueduct proper, on my long way back to Mexico City from Las Pozas almost a month later, I decided to stop at the pueblo magico of Zempoala and at Otumba to see more aspects and minor structures of the aqueduct. Well, let's say that in both towns the vast majority of people visit without any knowledge that there is anything of OUV to see (not that there is!). Same applies to the locals, some of which weren't even aware that Otumba and Zempoala had minor components inscribed on the WH list or where to find them. In a nutshell, even though the aqueduct is one of the least interesting WHS in Mexico, it doesn't make sense to skip visiting the aqueduct. I would have surely given the site a rating of 0.5 stars at best without visiting the aqueduct proper.