Mary Altaffer / AP

A contractor works on the East Side Access project beneath midtown Manhattan in New York.

Mary Altaffer / AP

Mary Altaffer / AP

Contractors work on the East Side Access project beneath midtown Manhattan, in New York. The East Side Access is one of three bold projects under New York that will expand what's already the nation's biggest mass-transit system by 2019.

Mary Altaffer / AP

Contractors work on the East Side Access project beneath midtown Manhattan in New York.

Mary Altaffer / AP

In this Tuesday, Jan. 29, 2013 photo, contractors work on the East Side Access project beneath midtown Manhattan, in New York. The East Side Access is one of three bold projects under New York that will expand what's already the nation's biggest mass-transit system by 2019.

 By Verena Dobnik, AP

Published at 3:07pm ET: NEW YORK - Sixteen stories below Grand Central Terminal, an army of workers is blasting through bedrock to create a new commuter rail concourse with more floor space than New Orleans' Superdome, just one of three audacious projects going on beneath New York City's streets to expand what's already the nation's biggest mass transit system.

But even with blasting and machinery grinding through the rock day and night, most New Yorkers are blithely unaware of the construction or the eerie underworld that includes a massive, eight-story cavern, miles of tunnels and watery, gravel-filled pits.

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Mohammed Salem / Reuters

A Palestinian worker shovels sand as he repairs a damaged smuggling tunnel dug beneath the Egyptian-Gaza border in Rafah, in the southern Gaza Strip on November 26, 2012.

By NBC News staff and wire reports:

Palestinians wielded shovels and planks Monday to reopen tunnels used to smuggle in goods from Egypt to the Gaza Strip after Israel's eight-day offensive against Hamas. Israeli airstrikes have heavily targeted the network of tunnels, which smugglers use to bring in various items -- including food, fuel, construction materials and weapons -- to Gaza's 1.6 million residents.

While many Gazans depend on the tunnels for basic food and supplies, the underground facilities have also been crucial to arming Hamas and other militant groups. Full Story

Mohammed Salem / Reuters

An excavator operates at the site of a destroyed smuggling tunnel dug beneath the Egyptian-Gaza border in Rafah in the southern Gaza Strip on Nov. 26.

Mohammed Salem / Reuters

A Palestinian smuggler waits for a cart containing gravel inside a smuggling tunnel dug beneath the Egyptian-Gaza border in Rafah.

Mohammed Salem / Reuters

Palestinians take a cigarette break as they work inside a smuggling tunnel beneath the Egyptian-Gaza border in Rafah.

Slideshow: Israel and Gaza: 8 days of violence

Bernat Armangue / AP

Israel's military said it had accomplished its objectives while Hamas claimed victory after the two sides exchanged deadly airstrikes and rocket attacks for over a week.

Launch slideshow

Related content:

• Gaza cease-fire raises hopes for reconstruction
• With truce holding, children in Gaza return to school
• Amid the ruins, Gazans say pity the living, not the dead
• Israel declares mission accomplished, Hamas claims victory

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ICE via AP

The unfinished tunnel discovered by authorities in Tijuana designed to smuggle drugs into the United States.

An Immigration and Customs Enforcement spokeswoman said Thursday that an approximately 220-yard passage, pictured at right, was lit and ventilated. It began under a bathroom sink inside a warehouse in Tijuana and did not cross the border into San Diego.

AP's report on the incomplete tunnel from Tijuana also mentions another found recently in Arizona:

Elsewhere, a 240-yard completed passage was discovered less than a week ago near Yuma, Ariz. U.S. authorities say that tunnel was operational.

As U.S. authorities heighten enforcement on land, tunnels have become an increasingly common way to smuggle enormous loads of marijuana into the country. More than 70 passages have been found on the border since October 2008, surpassing the number of discoveries in the previous six years.

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DEA via AFP - Getty Images

This image provided by the US Drug Enforcement Administration(DEA) on Thursday shows the US Entrance to a cross border tunnel linking a commercial building in San Luis, Arizona to Mexico that was discovered through a probe conducted by the DEA. The DEA on Thursday announced the details of a 240-yard (219m)passageway that was equipped with lighting and ventilation. US Justice Department officials say the sophisticated tunnel was used to transport drugs from Mexico to the commercial building on the Arizona side. Authorities said the investigation also included arrests and drug seizures.

DEA via AFP - Getty Images

The US Entrance to a cross border tunnel linking a commercial building in San Luis, Arizona to Mexico.

DEA via AFP - Getty Images

The cross border tunnel linking a commercial building in San Luis, Arizona to Mexico.

DEA via AFP - Getty Images

DEA image of 39 pounds(14.5kg) of methamphetamines recovered by officials from a cross border tunnel linking a commercial building in San Luis, Arizona to Mexico.

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