The railway authority has put forward two concepts - a visitor centre and viewing platform linked by a lift on the north side and a smaller base for more challenging guided walks to the top of the south tower.
A video outlining the proposals suggests a glass-ceiling centre could be tucked under the massive steel structure at North Queensferry, opening up a "cathedral-like" view above.
You can view the video below.
A lift would take groups to the top of one of the towers more than 100 metres above the Firth of Forth.
The second concept would allow public access from South Queensferry along an existing walkway under the approach span, close to Dalmeny Station.
Groups of 15 people wearing safety gear would then be able to take guided tours along the bridge all the way to the top.
The proposals would costs an estimated £12-15 million to deliver and could be "partially realised" by 2015, Network Rail said.
David Simpson, route managing director at the rail authority, said: "After 10 years spent restoring the bridge to its full glory, and in advance of the application for world heritage listing, these plans will offer the public the chance to visit the bridge and see it close-up for the first time. We are hugely excited by these proposals and believe that they have the potential to be developed into an important new visitor attraction for Scotland.
"While these plans are still at development stage, we believe that the options we have revealed today can be delivered without impacting the well loved view of the bridge. Any infrastructure on the bridge will be less visible than the existing scaffold platform and all buildings designs will be of premium quality.
"It's an ambitious target, but we'd love to see these plans at least partially realised by 2015 to coincide with the bridge's 125th anniversary. Any profits from the two facilities would be reinvested into the upkeep of the bridge. The bridge remains a key part of Scotland's railway infrastructure, linking Edinburgh with Fife and the north, and carrying over 200 trains per day.
"We are committed to working with communities, local authorities and relevant government bodies to develop plans that have a sustainable positive impact on the area. While we expect that visitor numbers will be high, we're committed to encouraging as many of those visitors as possible to travel by rail and we will develop plans alongside train operators to incentivise that option."
Transport Minister Keith Brown, speaking on behalf of the Forth Bridge Forum, said: "I welcome Network Rail's exciting and ambitious plans to combine an historic and vital part of Scotland's transport network with a breath-taking attraction for visitors to enjoy."