They stretch for scores of miles, over some of the most pristine land in Baltimore County.
They run along rivers and streams with picturesque names like Long Green Creek and My Ladys Manor Branch.
They are ribbons of land weaving through woods, cornfields and back yards that planners say will one day make up the Stream Valley Greenway Network, a vast collection of wooded trails and pathways along the county's waterways.
Baltimore County planners and park officials plan to put together the network "maybe over the next 50 years" by buying easements from property owners and accepting land donated by developers when they seek permits, said William Hughey, a community planner who oversees the project.
"It's a little like an Appalachian Trail," Joan Morrissey Ward, another community planner, said of the greenway network, which was approved by the County Council last February as part of the new master plan for growth.
The plan calls for a system of pathways throughout the county. They would link three of the county's major open space areas -- Patapsco State Park, Gunpowder State Park and the Black Marsh -- with trails that would allow a hiker to walk from the Patapsco or the Pennsylvania border to the Chesapeake Bay.
Since then, every developer who has come to the county with plans to build in any of the specified areas has been asked to donate the targeted land or grant an easement along the waterways, Mr. Hughey said.
Ms. Ward said the land sought by planners lies in areas where building would be prohibited by state and county environmental regulations that preclude construction near streams and waterways.
To back the plan, the Department of Recreation and Parks has budgeted some $355,000 for land acquisition and another $260,000 for easements over the next five years, Mr. Hughey said.
No money has been spent yet for acquisition, but next spring the county is expected to pay $150,000 for easements on a 2-mile stretch inthe Owings Mills area, Mr. Hughey said. He declined to be more specific about the location because he said negotiations are continuing.
The system's first path -- a 1.5-mile paved trail along the Gwynns Falls in Lochearn -- was established several years ago, but no others are planned to open in the immediate future, he said.
The county also has won agreements from eight developers and property owners to donate 75 acres at sites around the county, including tracts in Granite, Kingsville and Hunt Valley, Mr. Hughey said.
Liz Healey, president of the 500-home Kingsville Community Association, said she was pleased when planners won an agreement earlier this year for land to be set aside for the greenway network by the developers of Longfields, a housing development off Belair Road that straddles the Broad Run.
"It was great because it preserved open space in an area that badly needs it," she said. "It's a wonderful idea."
Mr. Hughey hopes to submit a proposal next spring to the county Planning Board that will detail where riding stables, camping sites and parking lots may be placed along the portion of the greenway system that weaves around the communities of Woodlawn, Owings Mills and Patapsco.
He said that portion of the plan, for the western corridor, will tie in with trails and open space areas that are already part of Patapsco State Park. Ms. Ward said that in many of the areas, there are already trails that were carved out years ago by hunters and fishermen. Such trails are frequently used by the public, even though they may be privately owned, she said.
"In many areas we're just following through on a plan for trails already being used and in place anyway," she said.
But Mr. Hughey said that although completion of the overall greenways plan is probably 50 years off, it will eventually mean additional public access to some of the county's most beautiful scenery.
"This is some of the most pristine and beautiful land in Baltimore County," he said. "If it's locked off to just private property owners, future generations will never know it exists."