PORTLAND — The Ohm Dome was the happening place at the city’s Urban Earth Day celebration Sunday.

The igloo-shaped structure, which was used as a spiritual meeting space at the Occupy Maine encampment at Lincoln Park last winter, provided one of the few dry and windless spots at the event on Monument Square, where rain fell and temperatures hovered in the lower 40s.

Despite the damp chill, a crowd showed up to inspect more than a dozen exhibits showcasing the city’s environmental and nonprofit organizations, sustainable businesses and others.

“This is a sign that Mother Earth loves us,” said Louisa Donelson, one of the organizers.

The celebration was organized by MENSK, a Portland group that promotes and supports creative and sustainable communities, and the city of Portland.

It was one of dozens of activities taking place across the state as part of a celebration that reaches worldwide.

The Urban Runoff 5-kilometer road race and Earth Day celebration at Deering High School in Portland raised money Saturday to support clean-water education in Greater Portland and Saco schools.

The West End Neighborhood Association in Portland held a Butt Bucket Brigade to pick up discarded cigarette butts.

Loon Echo Land Trust members scaled Bald Pate Mountain in South Bridgton to mark the day.

The first Earth Day was observed in 1970 to raise awareness and appreciation of the natural environment. Today, Earth Day is celebrated in more than 175 countries.

In Monument Square, Elizabeth Fraser of Portland and Maggie Knowles of Raymond made fresh kale, banana and berry smoothies. They are co-authors of “Kids Gone Raw,” an upcoming cookbook of raw fruits, vegetables and seeds for children.

“We are trying to make really delicious food available for children,” said Fraser.

Asanah Splude, 3, of Portland signaled her approval by quickly downing the brownish concoction.

“I guess she likes kale,” said her mother, Kristy Splude.

The city of Portland handed out spruce tree seedlings, and the Bicycle Coalition of Maine offered free, secure valet bicycle parking.

“You don’t need a lock, and it’s free and secure,” said John Brooking of Westbrook, a volunteer with the coalition.

Volunteers for Creative Trails, a community support group for adults with intellectual disabilities, took turns pedaling on a stationary bike that powers a blender to make smoothies. The bike will make a regular appearance at the Portland Farmers Market this summer, said Julie Carey, a Creative Trails staffer.

Back at the Ohm Dome, Nickie Sekera, manning the Occupy Maine booth, said it was cozy inside.

“It is really great in here,” Sekera said.

Staff Writer Beth Quimby can be contacted at 791-6363 or at:

[email protected]

Correction: This story was revised at 11:30 a.m., April 23, 2012, to reflect the correct spelling of Elizabeth Fraser’s name.