The protests began May 15 last year and drew hundreds of thousands of people calling themselves the Indignant Movement. The demonstrations spread across Spain and Europe as anti-austerity sentiment grew.

Spain is in deep economic difficulty, prompting fears it may need a bailout similar to those helping Greece, Ireland and Portugal. It is in recession, and unemployment stands at almost 25 percent — the highest among the 17 countries using the euro. One in two Spaniards under the age of 25 are out of work.

Prime Minister Mariano Rajoy's conservative government has enacted deep spending cuts to reduce the national debt, but many people blame those measures for deepening families' financial plight.

Javier Colilla, a 27-year old university student, said he showed up to protest in Madrid because Spain's economic situation seems like it will spiral into chaos.

"We've had this crisis for four years, but it feels like it's just starting," the fine arts major said.