Free Union Station walking tours: Get up close and personal with Denver's big dig

The rehabilitation of Denver's historic Union Station into a modern transit hub is one of the most complicated and ambitious projects ever attempted around here: a convoluted labyrinth of rail lines, bus infrastructure, pedestrian walkways and private development crammed into a crowded, historic corner of LoDo plagued with underground utility lines, low-level railroad contamination and stormwater drainage.

Now that construction has finally begun, want to see what all the fuss is about? Then check out the free walking tour of the project at 4:30 p.m. on the third Thursday of each month -- starting tomorrow, June 17.

The one-hour tour, hosted by the public agencies behind the redevelopment and beginning at the entrance of the historic train station, will recount the station's storied history and detail what's been called the largest transportation redevelopment project in North America. Some of the itinerary will focus on the underground bus terminal -- the first stage of the project that's already being excavated. Don't be surprised, though, if you don't see a lot of work going on.

Construction recently stalled after the discovery that the groundwater that workers had been pumping out of the site was contaminated with high iron content, meaning a new filtration system must be installed -- one requiring additional bureaucratic approvals. Officials hope to be up and running again in about a week - after the first installment of the free tour has already rolled though.

Still, there should be more than enough dirt -- figuratively and literally -- to ensure that the Union Station tour is time well spent. Just don't ask to drink the water.

Each tour is limited to 25 people; to reserve a spot, call 303-592-5462. If tomorrow's event is already full, you'll be able to sign up for next month's.