Registration shall be in Delhi where the property is situate. Section 28 of the Registration Act which is extracted below will throw you light.
28. Place for registering documents relating to land
Save as in this Part otherwise provided, every document mentioned in section 17, sub-section (1), clauses (a), (b), (c), 19[(d) and (e), section 17, sub-section. (2), insofar as such document affects immovable property, and section 18, clauses (a), (b) 20[(c) and (cc)], shall be presented for registration in the office of a Sub-Registrar within whose sub-district the whole or some portion of the property to which such document relates is situate.