If you're really interested in archiecture, one thing you should always keep in mind is that the moment the camera is tilted up from absolute horizontal, the building walls will start to look like it is falling over backwards. Unless the wide angle lens you get is a PC
(Perspective control) lens which are very expensive and no wider than 35mm.
That said, on all my foreign travels my absolute favorite lens (shooring film) is the Nikkor 20-35mm f:2.8 lens. It's gotten my out of many tight jams (sorry, bad pun) when I just can't back up enough. In addition, when travelling I simply won't leave home unless my Nikkor 16mm f:2.8 Fisheye is also in my bag. Yes, yes, yes.... I know. It distorts with lots of barrel distortion but I have some shots of building interiors where literally nothing else would do. When you need that all-encompassing feeling of being in a large cathedral etc., nothing but the fisheye will do.
If you want to check out some of my travel photos (Cuba specific) then here's the link. Also includes photos of some Cuban aircraft, civil and military.
Note it's a free hosted website and is bandwith limited per day. If you can't get in today, try again tomorrow.