Around 1,500 people objecting to controversial power and wind energy plans in mid Wales have gathered for a protest in Cardiff Bay.
Four campaigners against a network of pylons have ended a six-day walk from Welshpool, Powys, and have been joined at the Senedd by wind farm opponents.
Dozens of pylons, some measuring 154ft (47m), and a substation are earmarked to connect with about 10 wind farms.
The Welsh Government said it was determined to cut carbon emissions.
Politicians from the four main parties in mid and west Wales, including Montgomeryshire MP Glyn Davies, who called for the protest, were addressing the crowd in Cardiff Bay, and three petitions will be handed to the Welsh Government.
In 2005 the Welsh Government unveiled seven areas across mid and south Wales, known as Tan 8, which had been chosen for wind farm development.
In mid Wales, pylons could carry 400,000 volt electricity cables from north Powys to near Shrewsbury, Shropshire.
Tan 8 was part of the UK Government's energy policy to increase the amount of electricity from renewable sources to 10% by 2010, but Wales has exceeded this and produces about 13%.
Mr Davies compared the plan to the flooding of Tryweryn, near Bala, where a reservoir was created in the 1960s to provide water for Liverpool.
"If the assembly members who are here now allow this project to go ahead we want them to know that in half a century they will be remembered," he said.
"This is our Tryweryn and we are going to fight and they will be remembered if they carry on."
Addressing the protesters, weather presenter Sian Lloyd added: "Some people in this rather attractive building here want to destroy magnificent mid Wales.
"Are we going to let them turn rural Wales into one gigantic power plant?"
The Welsh Government said it was "determined to see Wales cut its carbon emissions and use more renewable energy".
A spokesman added: "As well as wind - biomass, marine and micro generation sources, all have their part to play.
"Our planning policy, informed by independent research, identifies seven areas for the development of wind farms to minimise the proliferation of large scale wind farms. We believe a small number of wind farms clustered in strategic areas is better than a large number of smaller wind farms across Wales."
He said all planning applications for wind farms were subject to a strict planning process which considered "their impact on the environment, and local community".
Nick Larder, 54, one of the four campaigners who started walking from Welshpool last Thursday, said they had received "massive support" along the route.
"There are lots of green solutions out there, but wind power is nothing to do with a green solution," he added.
Fellow walker Ifan Davies, 29, said: "Wind power only works on a local scale. It doesn't work on a national scale."
The National Grid urged people to take part in the public consultation process which has been extended until 20 June.
Wind turbines have long faced criticism from some local people, but complaints have grown since plans were unveiled for a 19-acre substation in Powys, and dozens of pylons.