"The bed is close to the desk."
Translation:Łóżko jest blisko biurka.
It's not exactly the same. Maybe the difference is not that visible in this sentence, but "blisko" can be used in a sentence like "Mieszkam blisko Warszawy" (I live close to Warsaw), and as it's pretty relative, this can mean that I live 50 km from Warsaw.
While "obok" is literally "next to", without much of an interpretation.