The paper discusses the properties and implications of extra-dimensional axions, which are modes of higher-dimensional gauge fields. These axions naturally arise in string theory and offer a compelling solution to the axion quality problem. The author argues that the axion decay constant \( f \) in such models is likely to be close to the fundamental cutoff scale of the theory, which is at most two orders of magnitude above \( f \). This is because axion strings, which are fundamental objects in these models, have tensions that scale with the instanton action \( S_{\text{inst}} \) and the decay constant \( f \), resulting in a tension of order \( 2\pi S_{\text{inst}} f^2 \). The paper also explores the physical characteristics of these axion strings, their masses, and their implications for the Strong CP problem and cosmology. Additionally, it reviews the existence of chiral fermions and their relationship with axions, emphasizing that tree-level mass terms are unlikely to remove light axions from the spectrum. The author concludes by highlighting the unique features of extra-dimensional axions and their potential experimental signatures.The paper discusses the properties and implications of extra-dimensional axions, which are modes of higher-dimensional gauge fields. These axions naturally arise in string theory and offer a compelling solution to the axion quality problem. The author argues that the axion decay constant \( f \) in such models is likely to be close to the fundamental cutoff scale of the theory, which is at most two orders of magnitude above \( f \). This is because axion strings, which are fundamental objects in these models, have tensions that scale with the instanton action \( S_{\text{inst}} \) and the decay constant \( f \), resulting in a tension of order \( 2\pi S_{\text{inst}} f^2 \). The paper also explores the physical characteristics of these axion strings, their masses, and their implications for the Strong CP problem and cosmology. Additionally, it reviews the existence of chiral fermions and their relationship with axions, emphasizing that tree-level mass terms are unlikely to remove light axions from the spectrum. The author concludes by highlighting the unique features of extra-dimensional axions and their potential experimental signatures.