An illumination system comprising at least one luminaire , the luminaire comprises: - at least one light-emitting semiconductor chip having a main emission side , and - a reflector having a reflection side facing the main emission side , the reflection side is a freeform different from a circle and ellipse and parabola and hyperbola when seen in cross-section, wherein - the luminaire is arranged on a wall or a pillar of a building which has at least in part a glass front, - the luminaire is arranged to illuminate a part of the building that protrudes from the wall or pillar, - at most 2% of the light emitted by the luminaire enters the building so that glaring within the building is avoided, - a base line (B) runs through the main emission side and a local height (h) of the reflection side is measured against the base line (B), - a local focal length (f) of the reflection side increases along the local height (h), concerning ray bundles (R) coming in parallel with the base line (B) from an exterior of the luminaire , - there is no common focal point (P) for all of the local heights (h), - the reflection side , when seen in cross-section, has the shape of a modified parabola, so that a distance of focal points (P) of the ray bundles (R) toward the reflection side along the base line (B) increases with increasing local height (h), - the base line (B) is in parallel with a mounting plane of the luminaire , the luminaire is mounted on the building with the mounting plane so that the mounting plane is on a side of the luminaire facing the building , - an angle between the base line (B) and a direction of maximum emission (M) of the luminaire is at least 2° and at most 15°, the direction of maximum emission (M) points away from the mounting plane , and - the base line (B) runs through the main emission side so that the base line (B) and the main emission side have a point (S) of intersection. - at least one light-emitting semiconductor chip having a main emission side , and - a reflector having a reflection side facing the main emission side , the reflection side is a freeform different from a circle and ellipse and parabola and hyperbola when seen in cross-section, - the luminaire is arranged on a wall or a pillar of a building which has at least in part a glass front, - the luminaire is arranged to illuminate a part of the building that protrudes from the wall or pillar, - at most 2% of the light emitted by the luminaire enters the building so that glaring within the building is avoided, - a base line (B) runs through the main emission side and a local height (h) of the reflection side is measured against the base line (B), - a local focal length (f) of the reflection side increases along the local height (h), concerning ray bundles (R) coming in parallel with the base line (B) from an exterior of the luminaire , - there is no common focal point (P) for all of the local heights (h), - the reflection side , when seen in cross-section, has the shape of a modified parabola, so that a distance of focal points (P) of the ray bundles (R) toward the reflection side along the base line (B) increases with increasing local height (h), - the base line (B) is in parallel with a mounting plane of the luminaire , the luminaire is mounted on the building with the mounting plane so that the mounting plane is on a side of the luminaire facing the building , - an angle between the base line (B) and a direction of maximum emission (M) of the luminaire is at least 2° and at most 15°, the direction of maximum emission (M) points away from the mounting plane , and - the base line (B) runs through the main emission side so that the base line (B) and the main emission side have a point (S) of intersection. <EOS>