The paper investigates the light rings, shadows, and gravitational lensing effects in a vacuum solution of General Relativity (GR) describing a Schwarzschild black hole (BH) immersed in a non-asymptotically flat rotating background, known as the *swirling universe* (SU). The SU is characterized by north and south hemispheres spinning in opposite directions, and it does not admit closed timelike curves. Using the Ernst formalism, the authors derive the metric for this spacetime and analyze the null geodesic flow. They find that there is one unstable light ring ($w = -1$) for each rotation sense of the background. The swirling background drives the Schwarzschild BH light rings outside the equatorial plane, displaying counter-rotating motion with respect to each other while co-rotating with respect to the swirling universe. Through backward ray-tracing, they obtain the shadow and gravitational lensing effects, revealing an odd $\mathbb{Z}_2$ (north-south) symmetry in the BH shadow, inherited from the same symmetry of the spacetime itself. This results in a twisted shadow. The paper also discusses the ergoregion, horizon geometry, and the topological charge of the light rings, providing a comprehensive analysis of the SBHSU spacetime.The paper investigates the light rings, shadows, and gravitational lensing effects in a vacuum solution of General Relativity (GR) describing a Schwarzschild black hole (BH) immersed in a non-asymptotically flat rotating background, known as the *swirling universe* (SU). The SU is characterized by north and south hemispheres spinning in opposite directions, and it does not admit closed timelike curves. Using the Ernst formalism, the authors derive the metric for this spacetime and analyze the null geodesic flow. They find that there is one unstable light ring ($w = -1$) for each rotation sense of the background. The swirling background drives the Schwarzschild BH light rings outside the equatorial plane, displaying counter-rotating motion with respect to each other while co-rotating with respect to the swirling universe. Through backward ray-tracing, they obtain the shadow and gravitational lensing effects, revealing an odd $\mathbb{Z}_2$ (north-south) symmetry in the BH shadow, inherited from the same symmetry of the spacetime itself. This results in a twisted shadow. The paper also discusses the ergoregion, horizon geometry, and the topological charge of the light rings, providing a comprehensive analysis of the SBHSU spacetime.