A phenylene macrocycle containing two meta-phenylene units positioned opposite each other was used as a building block to construct phenylene cages via platinum-mediated C-C coupling. A phenylene cage (PC[10]3), consisting of three phenylene macrocycle units, was successfully synthesized and thoroughly characterized using nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray diffraction. PC[10]3 exhibited significant backbone strain and displayed bright blue emission with a quantum yield of 96%. Additionally, PC[10]3 exhibited a broader and more pronounced piezofluorochromic response compared to its macrocyclic unit, undergoing a distinct photoluminescence shift from blue to yellow-green under pressure. This work opens new avenues for designing and synthesizing hydrocarbon nanocages.