Part 3/9:
Delving deeper, up to 100 cm underground, we find essential infrastructure like drainage systems and utility lines for electricity, water, and gas. These components, crucial for daily functioning, display a meticulous arrangement that has evolved with the city’s development.
In a fascinating twist, approximately 3.6 meters beneath the streets lies a small concrete obelisk—a survey marker from the 19th century. Officially called Benchmark A, this structure aids in monitoring ground movement, offering insight into the earth’s shifts directly under the Washington Monument. Interestingly, the ground beneath the monument has been steadily rising over the last century due to the swampy soil conditions.