The Vehicle Assembly Building at the Kennedy Space Center is huge and homely and almost 50 years old. It’s tall enough to house a 363-foot Saturn V rocket, wide and deep enough to dwarf a space shuttle, cavernous enough for its powerful cranes to maneuver the orbiter and its external fuel tank and solid rocket boosters into place on a mobile launch platform. By volume — 129 million cubic feet of space — it is the fourth largest building in the world: 525 feet tall, 716 feet long and 518 feet wide.

What this boxy building houses is even more impressive: the past and the future of the U.S. space program and the emotions that go along with that — nostalgia for the glory days of moon walks, pride in the space shuttle, dreams of a heavy-lift launch system that will take us deeper into space.

Space shuttle Atlantis, its tiles scorched by the heat of re-entry, is parked in one of the bays until next year, when it will become the centerpiece of an exhibit at Kennedy Space Center in Titusville. An Orion capsule — similar to the capsules used in the Apollo program, but bigger — just arrived, to be used in testing for the heavy-lift launch system, which is being developed to send rockets to the moon, to Mars or even an asteroid.

Next door in another wing is the Launch Control Center, where NASA supervised the launch of every Apollo and shuttle mission, the countdown clock ticking down the seconds, the launch pad in sight from more than three miles away.

The public has not been allowed into either space in more than 30 years. Now NASA is offering up-close tours of these and other facilities, using the gap between the end of the shuttle program and the start of testing for the heavy-lift system, while many of the facilities sit idle.

“It’s an opportunity … for the public to peek under the tent and get a look at these facilities that were built back in the ‘60s during the space race,” said Michael Curie, NASA spokesman at the Kennedy Space Center. “These were built for the Apollo program, then converted to launch the space shuttle, and now are being modified for a space launch system. It’s truly a unique opportunity.”

The newest tour, which started in June, is of the Launch Control Center, which houses four “firing rooms” that were the nerve center for each of 152 Apollo and space shuttle launches. Another tour, which started in November, goes inside the Vehicle Assembly Building.

Added to the other exhibits and experiences at the space center — a massive Saturn V rocket, suspended so visitors can walk under it; a view of the launch pads; the Firing Room Theater with the actual launch consoles used in the Apollo program; the Rocket Garden — the tours underscore the enormous scale of space exploration.

“There is a sense of wonder about these big pieces of equipment,” said J.R. Reilly, a retired astronaut who flew on three shuttle missions and now meets the public through the Astronaut Encounter at the space center. “Every once in a while, you need to stand under that Saturn rocket and see what a monster it is, to appreciate what it took to go to the moon and back in the 1960s.

“I like to call it the gee whiz factor. The Apollo was launched from here to go to the moon, and then we launched the space shuttle from here. Just the scale of it is pretty incredible.”