If one were, for example, near the Les Gobelins stop on the Paris metro, would they say "Je suis à Les Gobelins," or "Je suis aux Gobelins" ?
Same thing, another example sentence: "Je me souviens de Les Gobelins" or "Je me souviens des Gobelins" ?
You can use two sentence for this
Je suis à l'arrêt Les Gobelins
In this first sentence you specify what is "Les Gobelins". In this case it is a stop (arrêt). Use this sentence for formal conversation.
Je suis aux Gobelins
You can use this in a familiar conversation. The person you are talking with should know that Les Gobelins is a stop on the metro. If he does not know it, it may sounds weird for him and will not understand.