Algar do Carvao

Algar do Carvao is the throat of a volcano, opened up by a staircase so that you can walk down inside it. The entrance is a hole in the ground on Terceira's central plateau, and the descent leads through a chamber where rainwater has built silica stalactites, formations that grow differently from the limestone kind. At the bottom a clear pool collects, its level rising and falling with the rain. Daylight comes down the shaft from above and thins as you go, so the lower chamber depends on lamps. The site keeps short hours and closes altogether outside parts of the year, which makes checking before the drive worthwhile.

What you actually see

• The open shaft - daylight falling into the vent from the surface above.
• Silica stalactites - formations built from volcanic rock rather than limestone.
• The rainwater pool - clear standing water at the base of the chimney.
• The stairway - a long descent through the chamber to the floor.

When to go

Opening hours are the main constraint: the site runs on a short seasonal schedule, often afternoons only, and closes on some days entirely. Summer is when access is most reliable. Conditions inside are the same whatever the weather outside, which makes it a useful option on a wet Terceira day. Check the hours before committing to the drive.

Honest expectations

The visit is short for the ticket price, and the steps are wet, uneven and unsuitable for anyone unsteady. Humidity fogs camera lenses within seconds of entering. Opening hours are restrictive and change by season, catching out visitors who arrive unannounced. The interior lighting is dim, which is honest to the place but limits what you actually see.

Nearby

The Gruta do Natal lava tube, the Furnas do Enxofre steam field and Angra.