"There are cucumbers at the kitchen."
Translation:Sunt castraveți la bucătărie.
In this sentence, when "la" is used, one could understand that:
cucumbers are generally found in a kitchen, or
if you have Bucătărie instead of bucătărie, it could also mean that there are cucumbers at the restaurant (or market) called "Bucătărie" (Kitchen). This is the same case as in English when you use "at the" instead of "in".
If "în" is used instead of "la", then it means that the cucumbers are found inside the kitchen. In this case, you're being more specific about their location.
P.S.: I'm a native speaker and I very rarely hear someone say "la" instead of "în" in these situations.
Cu plăcere :)!
Also, one more rule regarding "la" or "în" which can be pretty useful:
when we want to say in which city (or place) we go, we always use "la": Eu plec la Londra/Madrid/București/Budapesta/Brasília/mare (seaside)/picnic/bunici (grandparents), and so on.
in the case of countries (or regions) we always use "în": Noi plecăm în Anglia/Africa de Sud/Brazilia/Nepal/Transilvania/Bavaria, etc.
You use "sunt în București" only if you live in Bucharest. If you used to live in Bucharest, and you are visiting, you're saying "sunt la București". If you are thinking to go in Bucharest, you say "mă duc la București". It could also have different meanings.., like: "V-a plăcut la București?" - (it means you are asking them generally it they enjoyed "different city/region" or not); if you ask "V-a plăcut în București?"- (it means you're asking for something particular, in might be in the centre of Bucharest).
hope this helps!
I agree with what Marius said about "la"/"în", with the addition that I would use "în" for being in a city (which should answer your question).
I am going to Cluj. - Merg la Cluj.
I am in Cluj. - Sunt în Cluj.
I would also use "în" in other contexts, such as:
Let's meet in Cluj. - Hai să ne întâlnim în Cluj.
(but I might also use "la" here).
The key here is that things aren't so fixed and you'll find differences and disagreements between native speakers. I am just one.
In your example, it is assumed that you're already in București (same as the kitchen example, when the cucumbers are in(side) the kitchen), and in this case we use "în".
In my previous example, I'm not in those cities/countries/regions yet (Eu plec/Noi plecăm - I/We go), and in this situation we have the rules when to use "în" or "la" described earlier.
One exception would be in the case of being (or going) at the seaside or a picnic.
- Eu plec la mare/picnic - I am going to the seaside/picnic.
- Eu sunt la mare/picnic - I am at the seaside/picnic.
In the last example, (even though I'm already at the seaside or picnic) we cannot use "în" like in your example (sunt în București) because that would literally mean inside the sea (underneath the water), or inside the picnic (this last example sounds weird :D)
In the end, there are quite a few rules when to use "în" or "la" depending on your current location, intention (you're going or not), places (seaside, mountains, ...), and so on.