Remote attacks can be from anywhere in the world and are rarely in the same geographic vicinity as the target.
This said there are a LOT of different ways your account could have been compromised and it may have nothing to do with your recent activities. If you use a patterned, or similar format, password on multiple websites your e-mail and password pattern could have been gathered from another site being breached. For example, if you use the following password on Yahoo:
and I know your e-mail address is with Google I might suspect your Gmail password is:
123google or 123gmail
simply from looking at another password you've used and your e-mail address. The timing could be a coincidence.
As another example of where it may have nothing to do with your activities, and I do NOT think your situation is a result of the following, but a while back Google was breached by Chinese Hackers (or at least that's who it's attributed to in the following article):
So right off the bat get rid of any thoughts that attackers need to be physically close to you to attack you on-line. Humans evolved to only be concerned about threats in their immediate proximity and it causes us problems when perceiving threats in the correct context on-line.
There isn't enough information in your post to step through all the activities you have done in the past with your account for anyone to really answer exactly how you were attacked but browser attacks, especially if you have used an older browser, and malware on all the systems you've used is certainly a possibility. If you've used any computers that you don't normally use those would also be likely candidates. Again there are thousands of potential possibilities but those are things I think most people would tell you to look at first.