The Hertz depot at Gare du Nord is located within the Gare du Nord terminal on level 1 with other car hire operators. Opening hours are

Mon: 0630 – 2330
Tues: 0630 – 2330
Wed: 0630 – 2330
Thurs: 0630 – 2330
Fri: 0630 – 2330
Sat: 0700 – 2330
Sun: 0700 – 2330