Canyon River Caverns
Minecraft Seed: 1898459172765565523
Go a little south from the world spawn until you see an acacia village up a hill, there is a river that flows through the center of the village and into the canyon. Canyon starts at 100x, 180z. Various inlets to the two cave systems on either side of the canyon, with a deep dark directly below the river.
Underground lakes, rivers, and waterfalls in the dripstone caverns, and an extremely long waterway/river going down the main canyon are only a small portion of what this seed has to offer near spawn. To the southwest of the canyon is a massive flower forest biome with its own mountainous river setting. The largest cavern is at -33x, 151z, with an opening at 78x, 241z
I recommend going into spectator mode to find everything available in the seed, as the list of interesting coordinates within 200 blocks of the center of the canyon is massive.