If you're interested in playing around more with this, it's using a standard called IIIF (https://iiif.io) for image access via API. It's used by many museums, libraries, and archives.

One of the benefits of this is that you can get access to a metadata file that lets you know technical information about the image: It's at https://iiif.micr.io/TZCqF/info.json.