PDF summary here: access to the Museum for a delivery.
When you arrive at the main entrance of the Estate (at the end of the “Drève de Mariemont”), ring the intercom and introduce yourself. The rising bollards are lowered. When the light (on your right) is green, move forward on the asphalt lane. When you come to a Y, follow the direction LIVRAISONS (deliveries), on your right.
Stay on the asphalt lane, the parking lot is further on your left.