Step 1: Modern cell culture rabies vaccines need a site with good muscle bulk and reliable absorption to mount a protective antibody titre.
Step 2: The deltoid muscle of the upper arm meets this requirement and is the recommended intramuscular site for older children and adults; the anterolateral thigh is reserved for infants below 2 years.
Step 3: The gluteal region is condemned because the thick fat pad leads to deposition in fat rather than muscle, lowering the immune response. Subcutaneous and abdominal wall injection are not part of the schedule.
Step 4: Both intramuscular and intradermal regimens default to the deltoid, making it the answer.
\[\boxed{\text{Deltoid}}\]