World's longest sea-crossing bridge finally opens : Video

Huge engineering effort

Built to withstand a magnitude 8 earthquake, a super typhoon and strikes by super-sized cargo vessels, the bridge incorporates 400,000 tons of steel -- 4.5 times the amount in San Francisco's Golden Gate Bridge.

It also includes a 6.7-kilometer (4-mile) submerged tunnel to help it avoid the busy shipping paths over the Pearl River Delta. The tunnel runs between two artificial islands, each measuring 100,000 square meters (1 million square feet) and situated in relatively shallow waters.

While an impressive engineering feat, the building of the bridge brought its own controversies. The Pearl River Delta is home to an endangered Chinese white dolphin population that has been buffeted by massive land reclamation efforts in Hong Kong and other cities.

Conservation experts previously told CNN they feared the bridge, as well as ongoing expansion of Hong Kong airport, could be the final nail in the dolphins' coffin, sending the local population into terminal decline.

In response to environmental concerns over the bridge, the Hong Kong government has provided for the creation of extra marine parks to protect dolphins and other aquatic life, but some experts say this may be too late to reduce the effect of the construction already carried out.

The bridge has also faced considerable public criticism over safety standards. Seven workers died in constructing the bridge, and another 275 were injured. Hong Kong officials have previously blamed the death toll on lack of manpower, and earlier this year a court fined several subcontractors over the issue.