Since every single travel site is an affiliate site there aren't many big sites to start as everyone is a rebrand whitelabel turnkey. All of these sites appear big so just find a dot travel site or any travel site in use if you want to see one. It is resellers driving the industry.
Done some research on reserved "visit" + city .coms, and met with a few .travel being used as the main website. I do admit I have a few on my list, but I don't like the registration fee...