This is a common and crucial question for any city gardener. The short answer is: it depends. Most well-designed urban planter boxes do come with pre-drilled drainage holes. This is a fundamental feature for plant health, as it prevents water from pooling at the bottom and causing root rot. You'll typically find these holes in standard terracotta, ceramic, wood, and many modern composite planters. Always check the product description or the bottom of the planter before purchasing.
However, some decorative or multi-purpose containers might not have them. Self-watering planters are a special case; they have a built-in reservoir and a wicking system, so they don't require traditional bottom holes. If your chosen box lacks drainage and isn't self-watering, you will likely need to drill holes yourself. Use a suitable drill bit for the material (ceramic, plastic, wood) and proceed carefully. Adding a layer of pebbles or broken pottery at the bottom before soil is an old practice, but experts now agree it's less effective than proper holes. For a thriving urban garden, ensuring adequate drainage is non-negotiable.