The tour began in the Western Wall Plaza, located at the foot of the Temple Mount. Judaism regards this as the place where God first created the world, and where the Divine Presence resides. According to the Bible, it was also the site where God told Abraham to sacrifice his son Isaac, and where Solomon built the First Temple.
The Western Wall has been under Israel's control since the 1967 Six-Day War, and remains a focal point of the Arab-Israeli conflict.
But the Islamic Waqf manages the Temple Mount itself, where the Dome of the Rock and the al-Aqsa Mosque are located. Muslims consider this the third most holy site in Islam.
The first ruins I saw were located to the west of the plaza. Here archaeologists recently uncovered a colonnaded Roman street, or cardo, dating back to the 2nd century C.E. Builders accidentally stumbled on these ruins in 2006, when the Western Wall Foundation tried to build a cultural center on this site.
Archaeologists believe that these were the homes of high-ranking Roman officials under the Emperor Hadrian, who established a pagan city in Jerusalem after the destruction of the Second Temple in 70 A.D.
This was probably someone's apartment or kitchen — an ancient Roman spice box was among the artifacts discovered here.
But the Roman ruins are just the beginning. Underneath the limestone paving, archaeologists found ruins that they believe date all the way back to the First Temple period, between 8th and 6th century B.C.
In other words, King Solomon, or his contemporaries, may have built this.
Here, archaeologists also found a signet ring inlaid with a Hebrew inscription that also may date back to the First Temple period.
The inscription may be a reference to a famous general from the Hebrew Bible.
According to the Israeli Ministry of Foreign Affairs, the inscription from the ring reads "Netanyahu ben Yaush," a possible reference to the Biblical general Netanyahu (yes, like the Israeli Prime Minister.)
Applbaum said that the ring was given to Prime Minister Benjamin Netanyahu, who keeps it over his desk.
The Western Wall Tunnel dates back 2,000 years, revealing the remnants of the massive retaining walls Herod built to support his expansion of the Second Temple.
Subsequent civilizations in Jerusalem built their cities on vaulted arches, keeping the Western Wall intact.
Excavations go down 15 meters, all the way to the foundation stones of the Western Wall. Applbaum hypothesizes that this work will eventually uncover stones from the First Temple.
Only 200 feet of the Western Wall are exposed above ground.
The other 1,591 feet of the Wall run underground, underneath Jerusalem's Muslim Quarter. The concrete pillars support the residential streets above the tunnel.
The most amazing site here is the Western Wall stone, the biggest of the "master course" stones holding up the Temple Mount. The stone — the largest in the Middle East – is 42 feet long, 11 feet high, 14 feet deep, and weights 570 tons. It is believed to be the biggest object ever lifted by human beings without machinery.
Further down the tunnel lies the most sacred spot on the Western Wall. This alcove, lit by oil lamps, is the closest place to the Holy of Holies, where the Ark of the Covenant was kept in the original Temple of Jerusalem. Judaism holds that this is where God resides.
Interestingly, this prayer area is mostly filled with women, many of whom sit here all day reading Psalms.
Back inside the tunnels, Applbaum showed me this Second Temple mikveh, a Jewish ritual bath that was likely used by people working in the temple 2,000 years ago. The bath is significant both because of its size (most mikvehs are a lot smaller) and its proximity to the Temple Mount.
Even more amazingly, that mikveh was built on top of another, smaller ritual bath, this one dating back to 2,200 B.C. Both baths were filled by natural spring water carried in from Bethlehem via aqueduct.
Just steps away lies Mikveh Hall, which houses another Second Temple ritual bath.
This ritual bath has been in continuous existence for 2,000 years.
A close-up of the ornate tiles in the Mikveh Hall.
A heavily-adorned room known as the Herodian Hall lies adjacent to the mikvehs. Although its ornate appearance suggests an important purpose, the hall was probably used as a changing room during the Second Temple period. Today, bar mitzvahs and other important events are hosted here.
Our last stop is the Hall of Ages, a hidden room discovered just three years ago, which contains archaeological discoveries from several civilizations. Each beam represents a span of about 500 years.
At the end of the Western Wall Tunnel, visitors can exit onto the Muslim Quarter. The opening of this exit in 1996 sparked massive riots in Jerusalem that killed 80 people.
But we exited back through the entrance. Here's Applbaum (right) giving the keys back to the spiritual director of the Western Wall.
Rand Paul spent a week in Israel....
