Beneath your feet lies a story millions of years in the making. Welcome to the Geomonumento da Rua dos Eucaliptos. This isn’t just a rock. It is a window into Lisbon’s ancient past.
The Geomonumento da Rua dos Eucaliptos is part of a city-wide project. It highlights Lisbon’s geological heritage. The project identifies areas of scientific, educational, and cultural interest. These become open-air museums called Geomonumentos.
Lisbon is built on diverse rocks. These rocks tell tales of different ages. There are fossil-rich limestones. There are basalt flows from ancient volcanoes. Also, there are deposits from rivers. Even landfill from after the 1755 earthquake is present.
Erosion has shaped Lisbon. It created the famous seven hills. Originally, there were only seven hills. But urban expansion increased that number to fifteen in the 19th century.
Here at the Geomonumento da Rua dos Eucaliptos, we see Grés de Grilos. This formation dates back to the Middle Miocene epoch. This rock formed during a regressive event. That means the sea level was falling.
Look closely at the base. It consists of coarse-grained sandstones. Above that, notice the brownish biocalcarenite layer. It is packed with fossilized bivalves.
Imagine this area 12 million years ago. It was a warm water beach. It teemed with life. Shell-producing organisms thrived here. Oysters and echinoderms were abundant. Their remains became part of the limestone. The erosion of these rocks created the sand you see.
Therefore, the predominant color of the rock here is brownish. You will find a layer of coarse sandstones. Its height is between 0.90 and 1.00 meter.
The Geomonumento da Rua dos Eucaliptos preserves a moment in time. It showcases the geological forces that shaped Lisbon. It is a reminder that the city’s story goes far beyond human history. Take a moment to appreciate the deep time. Consider the forces that created this unique place. This Geomonumento connects us to the Earth’s ever-changing story.