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How to Get Here
You'll find it at: Tower Bridge Road, London SE1 2UP, United Kingdom.
- By Tube: Tower Hill station (Circle and District lines) on North Bank and London Bridge station (Northern Bank branch and Jubilee lines) on the South Bank.
- By Train: For National Rail services, London Bridge Station is nearby on the South Bank, served mostly by Southern, Thameslink, Gatwick Express and Southeastern.
- By Bus: There are many routes to Tower Bridge and the surrounding area, so consult the official Bus Map by TFL.
- By Foot: It is close to other major attractions like the Tower of London and Borough Market.
About Tower Bridge
Tower Bridge is a famous Grade I listed bascule and suspension bridge built between 1886 and 1894. It was designed by Horace Jones and engineered by John Wolfe Barry. The bridge’s steel structure is mainly covered by Portland Stone (the main focus of this EarthCache), with some Cornish Granite towards the base of the towers (the focus of a nearby EarthCache https://coord.info/GCBTFDY).
Taken by LFC4eva on 10/26/2025 and Taken by BluePearl on 07/04/2025
What is Portland Stone?
Portland Stone is a type of limestone that formed about 145 million years ago under what is now the Isle of Portland in Dorset (for more information, watch https://www.youtube.com/watch?v=VtgX-b3BF7k) during the Late Jurassic Period. Back then, much of southern England was covered by a warm, shallow sea filled with marine life like shellfish, corals, and sea lilies.
Over millions of years, the shells and skeletons of these sea creatures piled up on the sea floor. Layers of sediment buried these remains, and pressure turned them into limestone. Portland Stone contains approximately 95% calcium carbonate, the same material found in seashells.
Fossils in Portland Stone
Portland Stone often contains fossils, preserved remains of ancient sea creatures. Common fossils include:
Bivalves: shellfish with two shells, like clams and oysters:
Gastropods: spiral-shelled sea snail:
If you look closely at the stone on Tower Bridge, you might spot these fossils. Weathering from rain, wind, and pollution over more than 100 years has sometimes made the fossils easier to see by wearing away the softer parts of the stone.
Weathering of the Stone
Weathering is the natural breaking down or wearing away of rocks. On Tower Bridge, you may notice signs like blackening, cracks, pitting, or worn surfaces on the stone (you will see less on the Cornish Granite towards the base of the towers, mentioned earlier). These changes occur due to factors such as acid rain, pollution, and natural ageing.
Why Portland Stone?
Portland Stone was chosen for Tower Bridge because it is strong, durable, and attractive. It has been used in many famous buildings, including St Paul’s Cathedral, the Cenotaph and the British Museum. Its ability to withstand weathering while showing beautiful fossil patterns makes it a perfect material for London’s environment.
Logging Tasks
AI Disclosure: AI was used for some of the research and writing of the cache page. The entire page was factchecked against the near endless archives on the construction of this famous bridge.
Please send your answers within two days. If not received, your Found It log may be deleted. You may log a Found It before receiving a reply. Either use the "Message this owner" button at the top of the page or use the Message Center.
- What colour is the stone?
- Is its surface smooth, rough, or grainy?
- What shapes or types of fossils can you see/identify?
- How do these fossils help us understand the ancient environment where this stone formed?
- Can you see any blackening, cracks, pits, or worn areas?
- What natural or human factors might have caused this weathering?
- Why do you think Portland Stone was chosen for Tower Bridge?
- Photo task: Take a photo of the bridge or the stone showing fossils or weathering. Upload these to your log if they don't include spoilers, or to your answer message otherwise.