Enormous spherical cavity inside Earth, hot air balloon floating in vast inner space, concave world surrounding in all directions, inverted landscape wrapping 360 degrees around viewpoint, central miniature sun suspended in the exact middle, no visible sky, Earth's crust visible as distant ceiling, multiple layers of floating landmasses at different depths, rivers flowing upwards and sideways defying normal gravity, forests growing perpendicular to curved inner surface, glowing crystals embedded throughout inner shell, other balloons visible at various angles including upside-down, steampunk-style balloon basket, explorers with surveying equipment, swirling mists and bioluminescent clouds, strange flying creatures circling central sun, hyper-detailed, epic scale, 8k resolution, photorealistic rendering