The concept of flux in quantum physics is connected to many intriguing phenomena such as the Aharonov-Bohm effect and Hofstadter butterfly. Particularly, flux in lattices with certain symmetries gives rise to many unprecedented phases of matter. Here, we report the experimental realization of two-dimensional photonic crystals featuring diverse synthetic $\pi$-flux patterns, achieved through harnessing the higher-orbital degree of freedom within confined-Mie-resonance photonic crystals. As a proof of concept, we fabricate two types of $\pi$-flux photonic crystals, and show that novel topological phases can emerge with peculiar optical effects, including a topological edge state with $4\pi$-period phase evolution, as well as two pairs of topological states which are localized at opposite boundaries but related by a nonlocal twist. These signatures characterize unambiguously a photonic Möbius insulator [an insulator with topological edge states with a $4\pi$-periodic sideband junction (like a Möbius ring)] and a momentum-space-nonsymmorphic symmetry characterized insulator, which remain experimentally unexplored to date. Our Letter opens the frontiers to explore the underlying physics between synthetic $\pi$-flux and photonic crystals.

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• Photonic crystals
• Photonics
• Symmetry protected topological states
• Topological effects in photonic systems
• 2-dimensional systems
• Microwave techniques