Denver Union Station was reborn in 2014 from a faded transit hub into the city's social heart — a vast Beaux-Arts hall full of leather sofas, a long bar, a bookshop, and a constant churn of locals on laptops who treat it as an office. Trains still run from the back (Amtrak's California Zephyr, RTD light rail and the A-line out to the airport), but you can spend an evening here without thinking about transport at all.
The Crawford Hotel occupies the upper floors. Around the building, the formerly industrial blocks of LoDo have filled in with restaurants and bars. Start an evening at the Terminal Bar inside the station, then wander into Larimer Square or down Wynkoop Street, both within a few minutes' walk.