A few months ago I would have said "sure, go for it, it will probably be fine!".
But now, as my pregnancy has gone past the 32 week mark, I am a bit more cautious, because by 32 weeks, going sightseeing was not an option for me.
Even the travelling would not have been ok, in my case, as thats when I was put on modified bed rest, which means no walking, no lifting, and just generally taking it easy.
Obviously, this is MY experience and not everyone feels the same, or has the same problems (Ive been having bad pain since 23 weeks, and really bad contractions since I was about 25 weeks, but managed to travel abroad at 26 to 27 weeks, my mobility was already a bit restricted, but it was fine).
Now at 36 weeks I can barely walk and even at 32 weeks would not have been able to do any sightseeing, as my back/pelvic pain and contractions would not have allowed for it.
So Id say hold off as long as you can, to see if you can make it. You will need a fit to fly form from your doctor (tyou need one from 28 weeks onwards)