The RTD rail system operates 365 days/year and most lines run from 3:15-4:30 am until 1:15-1:45 am. The "A" line runs from the airport to downtown Denver/Union Station and is only $9/way. From downtown, the "H" line travels to Colorado Station which is only 1.6 miles (or a 4 min/$5 Lyft ride) to the wedding venue. The "H" line costs $2.60/way or $5.20 for a day pass. If you'd like to take a Lyft from downtown it will be a 15-20 minute ride (pending traffic) and would cost around $15-$20.