5472 x 3648 px | 46,3 x 30,9 cm | 18,2 x 12,2 inches | 300dpi
Data acquisizione:
7 dicembre 2019
Ubicazione:
Manchester,North West,England,UK
Altre informazioni:
A manhole cover or maintenance hole cover is a removable plate forming the lid over the opening of a manhole, an opening large enough for a person to pass through that is used as an access point for an underground vault or pipe. It is designed to prevent anyone or anything from falling in, and to keep out unauthorized persons and material. Ancient Roman sewer grate made out of lime sandstone, 1st century AD, excavated at Vindobona (present-day Vienna) Manhole covers date back at least to the era of ancient Rome, which had sewer grates made from stone. Manhole covers are often made out of cast iron, concrete or a combination of the two. This makes them inexpensive, strong, and heavy, usually weighing more than 113 kilograms (249 lb). The weight helps to keep them in place when traffic passes over them, and makes it difficult for unauthorized people without suitable tools to remove them.
