Short answer: it depends on the planter, not on whether it is “urban.” Many commercial urban planter boxes are sold with drainage holes already drilled, or with knock-out plugs, grommets, or an overflow system. Others—especially decorative balcony boxes, indoor cachepots, and custom built-in planters—come without holes so they can be used as liners or to protect waterproof surfaces.
Before buying, check the product specification for terms such as “pre-drilled drainage,” “drainage holes,” “overflow,” “knock-out holes,” or “self-watering reservoir.” Look at close-up photos for holes, rubber plugs, or raised feet. If the planter is self-watering, it may not need holes in the usual sense; it should have a fill and overflow point instead.
If your planter has no drainage, you will usually need to drill it yourself unless it is designed as a cachepot. For plastic, use a sharp drill bit and support the base; for wood, seal cut edges; for metal, use a step bit; for ceramic or stone, use a masonry bit and take care to avoid cracking. A common approach is several 1/4–1/2 inch (6–12 mm) holes across the lowest points, not one central hole. Add a drip tray or saucer, keep the planter slightly raised, and make sure overflow will not stain or annoy neighbors below. If drilling is impossible, plant in a nursery pot with drainage and use the urban planter box as a decorative sleeve.