It's one of San Francisco's greatest works of street art — as good as anything Banksy ever gave this city, and certainly much, much bigger. The two giant seals that the artist known as ROA painted in the Mission District, onto a three-story building at 61 Bartlett, between 21st and 22nd streets, are in their final stages of life. A condo/retail project is going up on the property, and sometime in the next 16 months, ROA's seals will disappear. The seals have been there since 2011 — a stunning gift from a Belgian street artist with a global reputation for animal figures. Few other street artists have ROA's ability to orchestrate large, worldwide projects of such high artistic caliber. Now is the time to see the seals, while the property is still undeveloped and there are still great sightlines from Bartlett, the street that's just one short block west of Mission Street. Katie Wilson, a staff member at the property's development company, Build Group, says that the condo/retail complex will be eight stories tall and "will cover" the view of ROA's work when completed in January 2015. But the cover-up will probably happen months before then. In its literature for the complex, which will have 114 condominiums, Build Group describes the area as "the up and coming colorful Mission neighborhood." ROA's seals were a big reason the neighborhood had the kind of character that everyone now wants and then to eclipse it.