Entry door of the Nilometer - this structure is located on the island of Rhoda in central Cairo

Entry door of the Nilometer - this structure is located on the island of Rhoda in central Cairo

Exterior of the Nilometer - in Arabic it is known as al-Miqyas

Exterior of the Nilometer - in Arabic it is known as al-Miqyas

Interior of the Nilometer - this device was used to measure the levels of the Nile River

Interior of the Nilometer - this device was used to measure the levels of the Nile River

Decorative details on the walls of the Nilometer - this device has existed in the Cairo area since the Pharaonic Period but current structure was designed by Abu'l 'Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani

Decorative details on the walls of the Nilometer - this device has existed in the Cairo area since the Pharaonic Period but current structure was designed by Abu'l 'Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani

This part of the Nilometer would hold the Nile water so it can be measured -  If the water level was too low, there would be famine. If it was too high, it would be flood

This part of the Nilometer would hold the Nile water so it can be measured - If the water level was too low, there would be famine. If it was too high, it would be flood

This columnin the middle was a marker to show the levels of water and it is connected to the Nile by three tunnels

This columnin the middle was a marker to show the levels of water and it is connected to the Nile by three tunnels

Pit of the Nilometer - on left, two of the tunnels which would bring water to this pit, can be seen

Pit of the Nilometer - on left, two of the tunnels which would bring water to this pit, can be seen

These tunnels are now blocked off from the Nile River because the Nilometer is no longer functional

These tunnels are now blocked off from the Nile River because the Nilometer is no longer functional

Interior of the Nilometer is richly decorated

Interior of the Nilometer is richly decorated

Interior of this structure is adorned with Islamic calligraphy and motifs

Interior of this structure is adorned with Islamic calligraphy and motifs

Here three sides of the Nilometer and inner canopy can be seen

Here three sides of the Nilometer and inner canopy can be seen

A wooden beam on left is holding the top end of the measurement column

A wooden beam on left is holding the top end of the measurement column

Base of the measurement column - to measure the water level, the column is graded and divided into 19 cubits

Base of the measurement column - to measure the water level, the column is graded and divided into 19 cubits

One of the arches on side walls of the Nilometer

One of the arches on side walls of the Nilometer

Steps of the Nilometer - There are 45 of them which lead down to the bottom of the stilling well

Steps of the Nilometer - There are 45 of them which lead down to the bottom of the stilling well

Bottom of the pit - here the third tunnel (left) which is at the lowest level of the pit, can be seen

Bottom of the pit - here the third tunnel (left) which is at the lowest level of the pit, can be seen

Interior of the Nilometer - wooden beam crosses the structure in the middle thus dividing into two halves

Interior of the Nilometer - wooden beam crosses the structure in the middle thus dividing into two halves

Calligraphic details of the wooden beam

Calligraphic details of the wooden beam

The point where wooden beam is placed on top of the measuring column

The point where wooden beam is placed on top of the measuring column

Lower end of the canopy of the Nilometer

Lower end of the canopy of the Nilometer

Inside the Nilometer, there is a rectangular walkway. One end of this walkway gives access to the lower end of the pitt

Inside the Nilometer, there is a rectangular walkway. One end of this walkway gives access to the lower end of the pitt

One of the corners of the Nilometer

One of the corners of the Nilometer

Exterior of the Nilometer - sandstorms and air pollution are two major enemies of any structure in Cairo

Exterior of the Nilometer - sandstorms and air pollution are two major enemies of any structure in Cairo

A boat on the Nile just opposite the Nilometer - this boat is used for the entertainment purposes in the evening

A boat on the Nile just opposite the Nilometer - this boat is used for the entertainment purposes in the evening

Water of the Niles - the Nilometer is just on left of the small wall seen in this photo

Water of the Niles - the Nilometer is just on left of the small wall seen in this photo