Valentine Land (ハート世界, Hāto Sekai, Heart World) is an area accessible from the beating heart book in Heart World.
Valentine Land is a small, rather simplistic area decorated with various objects that appear to be made of stone, including curly organic-looking lamps, short vertical flagposts adorned with tattered pieces of cloth, and circular tables with bloodied hearts sitting upon them, one of which has long purple vines growing out of it similar to the ones found wrapped around the base of some of the lamps.
Entering from Heart World will place you infront of a book with a beating heart on it, which will take you back to Heart World if you interact with it.
There is a stone doorway to the northwest of the beating heart book that leads to a heart-shaped room, with 2 doorways at the top that both lead back to Valentine Land and a larger doorway at the bottom of the room that will take you to Sign World.
Just northeast of the stone doorway, a pink lineart heart can be found wandering around the area, which will take you to the Cyber Maze if you interact with it, and further to the northeast there is a spinning violet plant (directly below the beating heart book) that will take you to Elvis Masada's Place.
Nexus → Heart World → Valentine Land