Sure, here are some facts on manholes:

A manhole (also called a utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel.
Manholes are often used as an access point for an underground public utility, allowing inspection, maintenance, and system upgrades.
The majority of underground services have manholes, including water, sewers, telephone, electricity, storm drains, district heating, and gas.
Manhole covers are flat plugs designed to prevent accidental or unauthorized access to the manhole. They are traditionally made of metal, but may be constructed from precast concrete, glass reinforced plastic or other composite materials.
Manholes usually have metal or polypropylene steps on the wall to make it easier to get into the manhole.
Manholes are usually found in urban areas, in streets and sometimes under sidewalks. They are usually circular to stop the manhole cover from falling into the hole.
Manholes can be classified based on their depth as shallow, normal or deep. Shallow manholes have a depth ranging between 75 to 90 cm, normal manholes have a depth of 150 cm, and deep manholes have a depth greater than 150 cm.
Manholes can also be classified based on their material as plastic, precast concrete or fiberglass. Plastic and fiberglass manholes are commonly used where corrosion by sewer gas or infiltration and exfiltration are a concern.
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