Can I start setting up a completely new website without a domain?

Im sorry if this sounds dumb… but I do need your help! I have recently set up a website using WordPress. Can believe I actually did it – but its all working ok. I now want to set up a completely new website for a completely different topic. However, I would like to see how it all looks before buying a domain and host. Can this be done? I haven’t got a clue where to start and by no means want the 2 sites to be linked in anyway shape or form! I guess what I want is some sort of trail version where I can explore themes etc. Many thanks.