Visit the only museum devoted to ballparks themselves
A dented slab of the Green Monster
The National Ballpark Museum is a single-room collection in LoDo, across the street from Coors Field, opened in 2012 by Bruce Hellerstein and organised around the fourteen classic ballparks built between 1909 and 1921.
Why it's unique
Baseball museums are about players and games. This one is about the buildings, and it is the only museum anywhere given over solely to the ballparks themselves — their bricks, turnstiles, seats, signage, light fixtures, usher uniforms and vending equipment.
The object that justifies the trip is a section of the Green Monster, Fenway Park's left-field wall, carrying dents from 96 recorded ball strikes. Several were hit hard enough that the seams of the ball are still legible in the metal. Hellerstein's influence also reaches across the street: the retro brick entrance at Coors Field exists because he suggested it.
Before you go
It is small and it is one room, so an hour is plenty. Go before a Rockies game rather than instead of one.
Hellerstein is often there and will talk you through the collection if you ask, which is a materially better visit than reading the labels. Check the opening hours before travelling, because they are limited and tied loosely to the baseball calendar.