A sight is something you see.
The implosion of the old New Haven coliseum was an impressive sight. Or, in a compound form Let's drive to New Hampshire and do some sight-seeing.
A site is a place you visit, whether in meatspace or cyberspace.
We will be staying at the same camp site we were at last year. Or, the Delta web site has some handy information.
If you were looking at building lots, you might punningly say we're going site-seeing, but please only do this if you're an advanced user.
That is all, thank you. Please carry on. England Prevails.