Tens of thousands of Spaniards abandoned their customary quiet day with families and friends on Sunday to march against the so-called "Euro Pact" and the handling of the economic crisis.
In Madrid, marches began at six locations around the city, one at 6 a.m. from Leganes, 13 kilometres from the centre, before convening at the Neptune plaza in front of the Prado art museum, a stone's throw from parliament.
At 1200 GMT, police put estimates in Madrid at between 35,000 and 45,000 protesters, with no reports of violence, according to national radio.
"I'm here because this is a con," said Juanjo Montiel, 26, one of four blind protesters in Madrid, who works in Information Technology for around €1,000 a month.
"I'm lucky enough to have a job, but many don't and have no chance. And on top of that, the politicians want to make more cuts. This is not our fault, it's the system."
Sunday's protests have largely concentrated on the "Euro Pact", agreed by euro zone politicians to stimulate competitiveness across the bloc, which in Spain has prompted reforms to give companies greater power to hire and fire.
"The politicians have to come here and see this," said Paloma Cirujano, 30, a nurse in Madrid, marching with her 3-month baby in her arms. "This (movement) has to come to something. It won't just end here."
The protesters call themselves the "indignados", meaning the "indignant" or "outraged". Demonstrations first began before the regional elections May 22 in response to the perceived failure of politicians to represent the electorate.
The political leaders of the euro zone's fourth largest economy have worked hard to convince investors the country will not follow Greece, Portugal and Ireland in needing a bailout.
But Spaniards say while this has been happening, their own worries are being ignored.
Unemployment has soared to 14-year highs and almost half of under-25s are out of work. Banks have cut off credit lines, consumer prices are rising faster than the regional average, investment has been slashed and house prices have plummeted.
Meanwhile, the government has spent the last two years passing bills to keep wage rises to a minimum, lengthen working lives, abolish welfare payments and increase taxes.
Since May, the protests have snowballed.
In Catalonia, which has pledged to cut spending by 10 per cent this year, mass protests in front of Barcelona's parliament last week forced the region's president to be helicoptered in to debate where the axe would fall.