One last single-story building on one last stretch of undeveloped downtown Denver land will soon be razed and replaced by two condo towers. Over the weekend, Shelby’s Bar and Grill served its last beers at 519 18th St. The building that housed the bar for 28 years — and housed other bars going back more than 110 years — is getting torn down to make way for a 32- and 38-floor condo complex.