A good city guide will encourage his (or her) companions to look up when they are out and about on a walk. It is excellent advice - providing you don't forget to glance down now and again! Failure to do so could result in you missing some fascinating 19th century street furniture.
Coal holes were intended as entry points to a building's cellar. It was here where the fossil fuel could be delivered to a home with the minimum amount of fuss. As many of the apertures were incorporated into new residential developments for the wealthy, it would have been up to the domestic staff to distribute the dirty and dusty rocks to the numerous fireplaces around the property.
The circular covers (sometimes referred to as coal plates) vary in size but are mostly between 30-40 cm in diameter. Manufactured of cast iron; it is not unusual to find some that include cement and glass panels. An internal locking-system ensures that no access to the bunker can be made from above.
The plate designs often reflect the house styles of the foundries responsible for their creation. Largely redundant today, the condition of the surviving coal holes differ from location to location but are well worth looking out for.