i couldn't pick just one because i am interested in, as a dear friend once said, EVERYTHING! History, science biology and neurobiology, psychology, art and artists. So of course there are events i'd love to be able to take extended peeks at the reality of like the Algonquin Roundtable or the gatherings of American ExPat artists in France post WWI or certain crucial moments in history--when those in power considering choices that would impact us all, i'd want to know their thought processes at the time. (Not what just they put in memoirs or biographers put in books about them.) i like certain decors, designs, fashions but if you have the courage--wear/use/drive whatever serves your purposes and is comfortable gives you joy no matter what era it comes from.
But i wouldn't want to live any other time but right now, here/now is where i make the choices i need to make for me.
i have to smile when people romanticize the past, because people mistakenly think positive thinking is just seeing the world thru rose colored glasses, painting silver linings around every cloud but anyone who indulges nostalgia for past eras (a little for our own life and times is unavoidably human) is usually ignoring (denying?) the realities of daily life for most people in those times. The movie Midnight in Paris addresses this very well, when a time-slip allows a modern screen writer to visit the gatherings of ExPat artists i spoke of in first paragraph.
Why i wouldn't want to visit future and come back is a whole other discussion.