Abstract: Agricultural and/or horticultural greenhouse for cultivating crops therein, wherein the greenhouse is provided with a ventilation system comprising air displacing means for drawing in air in the upper part of the greenhouse, and wherein the ventilation system is adapted to displace the indrawn air in at least substantially vertical direction in the direction of the lower part of the greenhouse, wherein the ventilation system also comprises at least one substantially tubular air duct for guiding the indrawn air from the upper part of the greenhouse in the direction of the lower part thereof.