Lin-Manuel Miranda seems like a pretty fun guy, so it’s no surprise that his trip through the humdrum, fluorescent-lit bowels of the U.S. Capitol on Wednesday turned into a roving musical adventure.

Miranda, the Tony Award-winning creator of the hit musical “Hamilton,” was in Washington this week to receive the U.S. Capitol Historical Society’s 2017 Freedom Award. On Wednesday, he took to Capitol Hill to lobby on behalf of the National Endowment for the Humanities and the National Endowment for the Arts.

And in the process, he took a few rides on the so-called “Secret Congress Train.”

In videos posted on his Twitter account, Miranda offered a behind-the-scenes look at the Capitol subway system, a network of trolleys in the basement of the Capitol that lawmakers use to travel between Senate and House chambers and their offices in adjacent buildings.

While zooming through the Rayburn tunnel in a members-only car, Miranda sat alongside his father Luis A. Miranda Jr. and Rep. Adriano Espaillat (D-N.Y.), channeling the closing salvos of “My Shot” from Hamilton.

On the enclosed Senate subway that leads to the Dirksen and Hart buildings, Miranda tapped into some old-school showtune vibes with the “The Trolley Song” from “Meet Me in St. Louis.”

And on the train to the Russell office building, he did his best rendition of “Ol’ Man River” from “Showboat,” as fans waved in the background.

And of course, there was “Oklahoma!”

But despite Miranda’s nickname for the subterranean trolleys, the “Secret Congress Train” is not actually very secret. The trains — one line on the House side, two lines on the Senate side — are open to members of Congress, Hill staffers and registered lobbyists, who can bring along guests for meetings or tours. (The trains used to be open to anyone visiting the Capitol, but security rules were changed after the Sept. 11, 2001 terrorist attacks.)

The train tracks themselves are pretty short: The longest line runs between the Capitol and the Dirksen and Hart office buildings, and it stretches less than a third of a mile.

But despite its modest size, the Capitol subway system has played an outsized role in congressional goings-on over the course of the century that it’s been in existence, as reported in a recent Washington Post story:

The subway and its adjoining no-frills, fluorescent-lit station platform have long been a gathering place for the swarm of Capitol Hill journalists, aides and lobbyists who aim to pounce on senators as they disembark from trams or hitch a ride in the same car as a fellow lawmaker, hoping to bend an ear for the 90-second ride from one station to another.

It was invented in the early 1900s to ferry people back and forth between the Capitol for votes, which happens several times per day.

The tunnel to the offices first featured electric Studebaker automobiles; later, officials switched to trains on tracks out of concern that a lawmaker would one day get mowed over by a careering car.

After multiple rounds of expansions and upgrades, there are now two types of trains on the Senate side: an open-air tram to the Russell building driven by operators who ping-pong back-and-forth all day, and a Disneyland-style driverless train that runs from the Capitol to the Dirksen and Hart office buildings.

Despite the fact that the underground trolleys are a routine part of the daily lives of lawmakers, the Capitol’s transit infrastructure still evokes a strong response from visitors. And unlike Miranda’s apparent delight, not all of the responses are positive.

Back when the tunnels were first built, such an investment in infrastructure for a rarefied few seemed excessive.

And now, to many, it still seems like an excessive expense. But [Senate historian emeritus Donald A.] Ritchie defended the system.

“If the Capitol had been designed as a 60-story building, you’d have a bank of elevators and you wouldn’t be surprised,” he said.

Over the years, the Capitol subways have served as veritable who’s who of both lawmakers and celebrities. Jon Stewart made an appearance in 2015. And Miranda himself made a previous appearance on the trains back in 2016.

The Capitol Hill subway was built to quickly take lawmakers from their offices to the Capitol, but it's become a hub of political drama, especially in recent months. (Claritza Jimenez/The Washington Post)

Miranda also has done musical transit selfies before: Check out his videos from back in the day of riding the New York City subway system.