Yes. Many urban planter boxes are now made as modular systems, so you can stack units vertically, connect them side by side, or do both to fit a balcony, patio, rooftop, or courtyard. The key is to choose a system designed for the way you want to use it. Stackable planter boxes usually have reinforced bases, locating pins, or recessed tops that let one unit sit securely on another. Connectable planter boxes use side clips, bolts, dovetail joints, or interlocking edges to form longer runs or L-shaped layouts. Some brands sell connector kits separately, so check what is included before buying.
Modularity is useful because it lets you start small and expand later. You can create a vertical herb garden on a small balcony, connect several troughs along a wall, or separate units when plants need more space. For urban settings, look for weather-resistant materials such as powder-coated metal, UV-stable polypropylene, recycled composite, or timber treated for outdoor use. Also check drainage: stacked units need clear water flow and drip trays so upper planters do not waterlog lower ones or stain the surface below. If you plan to connect boxes, confirm that drainage holes and irrigation lines can be aligned without leaking.
Before stacking, check the load rating. Wet soil is heavy, and a planter that is easy to lift when empty may be too weak when filled. Use lighter potting mix, avoid tall stacks in windy exposed sites, and secure the system if needed. For connected planters, think about access for pruning and harvesting, and leave room for expansion. A modular planter system works best when you use the same brand and series, because connectors, trays, and accessories are more likely to fit.
In short, yes: modular urban planter boxes are widely available in stackable and connectable designs. Choose interlocking planters with strong connectors, reliable drainage, and a realistic load rating, and you can build a flexible urban garden that grows with your space.