This is the 6124th most frequent Russian word.
странно
Strangely; odd; weird.
In this sentence, "странно" is used as an adverb to describe an unusual or unexpected situation, specifically the act of observing someone in an uncommon location.
Это было странно видеть его в таком месте.
It was strange to see him in such a place.
Here, "странно" expresses the speaker's sense of surprise or confusion regarding someone's actions, functioning as an adverb.
Мне странно, почему он так поступил.
It seems strange to me why he acted this way.
In this example, "странно" takes the form "странная" to act as an adjective, modifying the noun "ситуация" to describe its unusual nature.