Lagoa das Sete Cidades, Volcanic crater lake in São Miguel, Portugal

Lagoa das Sete Cidades is a volcanic crater containing two connected lakes within a caldera, where one displays distinctly blue waters and the other green waters. The entire formation reflects how volcanic forces shaped this landscape over geological time.

This volcanic crater began forming over 200,000 years ago through a series of eruptions that created the large caldera structure. These volcanic events established the foundational landscape that visitors observe today.

Local people share an old story about a princess and a shepherd whose forbidden love caused tears that created two lakes of different colors. This romantic tale remains woven into how visitors and residents understand and talk about this place.

Several viewpoints around the crater rim are accessible via hiking trails from multiple starting points. Wear good footwear and allow extra time to visit different viewpoints for the full perspective on both lakes.

The two basins are hydrologically one lake, separated by a shallow channel crossed by a low bridge. The Green Lake's phytoplankton, dominated by cyanobacteria, persists year-round, while the Blue Lake's populations vary seasonally. High cyanotoxin levels were measured in the Blue Lake in 2002.