A vibrant cityscape built on a colorful rainbow, with streets and buildings adorned in an array of bright hues. The city’s architecture is whimsical and playful, with structures that seem to float atop the rainbow’s arc. The streets are bustling with life, featuring a mix of futuristic and fantastical elements, as pedestrians walk along the vibrant paths. The rainbow stretches across the sky, creating a magical atmosphere that blends seamlessly with the urban environment. The overall composition is filled with bold, saturated colors, capturing the energy and creativity of a fantastical world where architecture and nature coexist in harmony.