Portugal
A small volcanic crater islet and its surrounding protected waters off the south coast of São Miguel, near Vila Franca do Campo, designated a Natural Reserve since 1983.
Formed by a surtseyan tuff cone with a circular crater about 150 m in diameter, the islet was declared a Natural Reserve in 1983, with protection extended in 2004. It is a BirdLife International Important Bird Area (Cory's shearwaters). Diving takes place inside the crater and along outer walls; as of 2025 access has been restricted to certified local operators with a daily visitor cap. Source: Wikipedia (Vila Franca Islet), turismo.azores.gov.pt.