Dumb Question but.....

No question is dumb.
/waits for igazor

When a save is deemed "bad" by the game, it means that it is not complete or has gone corrupt. Not complete means that the system ran out of usable resources during the save process (usually resulting in an Error12), so data that could be critical to the running of that save again would be missing. Corrupt means that data has been deemed to be landing in the wrong places thus providing a game that if loadable would be all mixed up or just wouldn't run properly; once this starts happening the data corruption tends to just get worse. Think of a saved game as a tremendously huge spreadsheet or database, where much of the data is garbled or unfortunately landing in the wrong columns.

In theory, yes one can remove the .bad suffix and try to load a bad save. No harm would come to our computers, but chances are that the save just wouldn't load or it would be total garbage to play. If the goal is to get the save loaded just long enough to extract let's say one sim or household from it, then the extracted elements could still be incomplete or corrupt and mess up another game session/save into which they may be inserted. I would never risk trying this.

And sorry, one has to work pretty hard to find or construct them but there are examples of dumb questions (this isn't one of them). Here's a few:
"How long is a piece of string?"
"Answer me please, are you asleep?"
"What is the actual point of drinking coffee"? (this one is admittedly a bit subjective)
"Why does (sibling's name) get to do everything just because they are older?"
:)

Your game just runs out of memory. Make sure you use a freshly started game before you travel, and after you arrive, save once more and restart the game again. This usually shaves off a few 100 MB of used memory.

I haven't tried Setra yet but heard that it's just a little bit too big for its own good.

No, restart the same save you just produced. Not the bad one, of course. For example, if I travel to China from my Sunset Valley, my memory usage is usually close to 3000 MB. Note that saving itself has the potential to increase memory usage by several hundred MB, and my game tends to fail around 3250 MB. If I save, exit the game, restart and load that same save again, it's somewhere like 1750 MB (in China; SV is a lot more).

If you meant what to do in your current situation, you should revert to the last save before the bad one. Maybe, clean that one out.

I'm not familiar with the sim version of Barcelona, but it should be noted that Setra is an example of a beautiful custom designed world that is just too large and intricate to run properly. Another popular example of such a world is Alpine County. But we can overload just about any world by shoving too much content and too many sims into it. TS3 is a 32-bit only application and can only address up to 4 GB of RAM (the actual limit is ~3.7 GB). One spike into or above the danger zone, which is around 3.5 GB for most of us, and the game will lose its mind if it tries to reach for more and continue. The actual saving process will spike RAM usage up a bit as it runs.

Of course the player must have enough RAM installed and free for use (not being taken up by other applications at the same time) to work with properly. But we cannot improve upon the built-in limits of 32-bit applications no matter how much RAM the player has installed. We can advise all kinds of ways to help stay under that limit, but I'm afraid one of them is don't play in worlds that are too overwhelming for the game to handle.
http://www.nraas.net/community/TIPS-FOR-BETTER-GAME-PERFORMANCE

In case my comment about cleaning your save triggered this, this is not what I meant.

Anyway, it's safe to remove any world you never intend to visit again from your savegame. The game will create a completely new copy if you ever decide to go there again, of course without remembering you ever were there.

@KatyFernlily - I didn't say the questions didn't have any possible or even reasonable answers (your # 2 seems like more like a creative version of the truth than an answer though). But they do not impart the notion of the one asking being overly informed about how life works in general, child or otherwise. Would you like some more examples?

"How long does it take to drive from Detroit to Michigan? (for those who might not know, Detroit is a city in the state of Michigan already)
"If this escalator breaks down while we are standing on it, how are we supposed to get home?"
"If an airplane crashes right on the border between two countries, where do they bury the survivors?'
"What is the Ultimate Question of Life, the Universe, and Everything for which the answer is 42?"

If you have little space on your computer, that would affect your Sims game, right? I just had to delete and clear up a ton of space on my computer this morning.

I guess here the answer to the Ultimate Question of Life, the Universe, and Everything, for which the answer is 42, might be a good ballpark for the goal to shovel free. In GB.
Or maybe a little less.

I hope you are just teasing me, igazor :'(
Or I'm not very funny.
(I'm from Michigan)