download High Sierra without installing?

Currently running Sierra (10.12.6) on late 2015 iMac. Is there a way to download High Sierra and save it to disk without installing it?

I clicked on 'open' in the Application Store, and proceeded to click install, agreed, continue, and now the window says 'ready to install' and prompts me to click restart to install.

I actually don't want to install it right away. Has the system been downloaded to my hard disk? Where should I look for it?