The "Lagoon of the Seven Cities" is a pair of crater lakes that share a single basin but appear in two colours — one blue, one green. They sit inside the caldera of the dormant Sete Cidades volcano, five kilometres across, with the village at the western end. The lakes cover about four square kilometres and reach 33 metres at their deepest. Trout and pike have been introduced, and you can hire a kayak or pedal boat at the small dock by the village.
The full lakeside is not walkable — the northern shore is too steep and unstable — but the easy loop along Lagoa Azul takes about an hour and includes a stone bridge between the two waters. The view that is on every Azores postcard is from Vista do Rei on the southern rim, where on a clear morning both colours show side by side. The crater itself is geologically young, with eruptions as recent as 1880, and steam still vents through cracks in the lake bed.