thanks everyone. milan and pete, this is a trick that i found when i was learning the hdr blend in lightroom. i'll try to write it up better and with screenshots.
you have to plan for this when you take the shots. so camera on the tripod, same exposure settings and focus. note where your people are in the first shot and shoot when they move out of that spot. rinse and repeat.
my old method would be to process the files exactly the same in lightroom, export them as jpgs and load in photoshop. then stack them in layers (many ways to do this but i used edit>automate>stack as layers or something like that). add masks to them and mask out the people.
my new method (lightroom 4.2 and cs6) is to select all of the photos in lightroom before editing. right click - edit in>stack as layers in ps. add your masks, mask the people out. then just close the file, it reloads the image back into lightroom and lets you edit the image as you would any other raw file. but now you can see all the details in one frame minus tourists.