Identify the subject of the following sentence:
Walking through the lovely garden outside the children’s wing of the clinic relaxes me on a stressful day.

The subject of the sentence is "Walking." It is the gerund form of the verb "walk" and functions as the subject of the sentence. The action of walking through the lovely garden is what relaxes the speaker on a stressful day. The other options, "Children's wing," "Garden," and "Me," are not the subjects of the sentence but rather other elements within the sentence.