What cactus can grow up to 6 feet indoors?

The San Pedro cactus (Echinopsis pachanoi) is a popular choice that can grow up to 6 feet indoors under the right conditions. It prefers bright, indirect sunlight and well-draining soil, making it suitable for indoor environments. Proper watering and temperature control are essential for its growth. Additionally, its fast growth rate makes it a striking addition to indoor plant collections.