Balaban Island is a small nature conservation area just north of the bridge on the eastern shore. It is a quiet side-branch landscape of old trees, water, and birdlife, part of the low-key river scenery that makes Ráckeve more than a church-and-castle stop.
Treat it as a short walk rather than a major excursion. It works best after the town sights, when you want to see the slower Danube edge.