Allowing me to Visit your Facility
Please allow me to extend my appreciation to you for allowing me to visit your __(facility/office/shop/etc.)__ recently. You run quite an impressive __(factory/operation/business/etc.)__ over there.
What a great opportunity it was for me to learn more about the __(Name/make/model of equipment)__. In particular, I was fascinated to learn that __(briefly describe an area that you found fascinating)__. I now have a much better understanding of how to fully integrate it into my own business. After seeing it in operation, I have to say I hold a whole new respect for the complexity of the __(type of equipment/system)__.
Thank you again, __(Name)__, for generously affording me __(length of time/i.e. an hour)__ of your valuable time. It was a most enlightening experience and I will not forget your generosity.