The Enoshima Oohashi Bridge connects Fujisawa and the Kamakura Area in general with Enoshima Island in Japan. In both versions of the Elfen Lied series, it is a critical setting for climactic and pivotal moments centering around Mariko Kurama.
In The Manga
In the manga depiction, it is difficult to tell that the bridge is in fact two separate structures, one for each direction of foot traffic. It is first fully seen when Mariko arrives in the area with Shirakawa and Isobe, only for Nana to meet them, having sensed Mariko's presence, also wishing to keep this threat away from her new friends at Maple House. The bridge becomes the focal point and center of this story arc. Nana quickly finds herself overwhelmed by Mariko's far greater power, suspened nude above the bridge until Mariko's taunts rile Nana to retaliate and disable her foe. Two other factions moved in from different points. From the Fujisawa side of the bridge, Kouta arrived with Nyu in tow, seeking to find Nana, who had not returned for dinner as promised. However, a police blockade kept them back until Nyu jumped it, bypassing the concerned Kouta as well as the police. On the other end, Kurama arrived in the company of military officers and hardware, possibly sent by Kurama's then-unrevealed allies in Saseba. In the interim, Mariko killed Isobe and Shirakawa returned to the Diclonius Research Institute, revealing in the process that she was a spy set to stop the plans of Chief Kakuzawa. Despite cuts to Maple House and flashbacks to Kurama's past, the bridge (presumably the side leading from Fujisawa) remains the first and almost only location.
The bridge sustains numerous attacks but appears to show no real or extensive damage. At one point, Mariko is struck by a no-yield missile which dents the ground but does not break the bridge. Mariko herself at last explodes due to the embedded bombs placed inside her body, but aside again from the ground, only the attacking Lucy is disabled by this. If the bridge is seen again in series, it is never shown from the same wide shots as depicted in Mariko's story. Technically, it must have been accessed in the manga finale, as it would be needed for some characters to reach the nearby Sea Candle, the site of the series' final events.
In The Anime
The anime clearly shows the bridge to have two sides or lanes, both in perspective and in close shots. The bridge is attacked less during similar scenes to the manga, but actually takes more visible damage.
One major difference is that Kouta follows Nyu onto the bridge, after inexplicably finding the police at the Fujisawa side of the barricade unconscious. Kouta is threatened by Mariko, who is jealous of Nana's having a friend. In protecting him, Nana is repeatedly sent against the railing until it gives way, with Nana falling into the water below, where she is found by Kurama. When Isobe defies Shirakawa and fires upon Kouta and Nyu, Nyu gives way to Lucy, whose vengeance on the soldiers, and in particular Shirakawa, brutally awakens Kouta's lost memories, which in this version are regained on the bridge, not in Maple House. At one point during the battle, Lucy switches lanes by levitating, using her vectors, so she can avoid one set of attacks, only to fly back again, landing in the midst of the remaining soldiers, where they cannot fire upon her without hitting each other.
It is also on this bridge that Lucy leaves the series, her exact anime fate unknown, as she faces down one last wave of SAT soldiers, one horn already lost to Mariko, and another seen flying off amidst gunfire.
In either version of the series, pivotal events take place on this bridge. In the case of the anime, they are concluding events, barring further anime episodes emerging. In the case of the manga, they are transformative events, concluding the second part of the series and beginning the manga's more decisive - and to some fans, divisive - finish.