Built on the site of the old Union Pacific Railroad Depot, Jackie Gaughan’s Plaza is a 1970s time capsule. Like most downtown joints, the down-at-heel Plaza is made for low-rollin’ gamblers. Its tacky decor doesn’t correspond to any known theme, unless the theme is cheap. And that’s just fine with the Plaza’s patrons, who are hypnotized by the penny slots, nickel video-poker machines and $1 blackjack tables with sarcastic dealers. Feisty blue-haired ladies play for keeps upstairs in the 400-seat bingo room. Also upstairs is Firefly, a tapas bar with cockpit views of the Fremont Street Experience.