You know you’re headed someplace unique as you approach the Observatorio de Arecibo (end of Carr. 625, Arecibo, 787/817-1936 or 787/880-7420, www.naic.edu, Wed.–Fri. noon–4 p.m., Sat.–Sun. and holidays 9 a.m.–4 p.m., $4 adults, $2 children and seniors), the world’s largest and most sensitive radio telescope.

The bustle of commerce, industry, expressways, and road-construction projects eventually gives way to a bright green grassy landscape dotted with dramatic haystack-shaped hills called mogotes. Passing cars become few as the curvy road winds around the hills and ever upward, past sprawling cattle farms and errant chickens.

Be sure to bring sturdy walking shoes and an umbrella. Entry to the observatory requires a half-mile hike—mostly up stairs—from the parking lot to the entrance, and there’s little shelter along the way. As you climb ever higher toward the observatory, the first glimpse between treetops of the telescope’s suspension apparatus is a startling sight. Its cold, clinical, metal construction is in sharp contrast to the wilderness that surrounds it.

The road ends at a guardhouse, where you park your car and begin the long uphill trek on a concrete surface to the top of the massive sinkhole that contains the telescope’s dish. There are 500 steps, according to one source, and the hike can be so steep and arduous that there are little covered resting stations along the way for those who need to catch their breath. Visitors unable to make the journey by foot can get permission from the guard to drive up to the entrance.

Because there’s not really much to do on a tour of the observatory, other than gawk at the sheer size of the telescope dish, a newly constructed educational center has been added. Inside are two levels of informative displays and interactive exhibits that educate visitors on the finer points of the study of space and the atmosphere. A short film on the telescope is screened throughout the day in both English and Spanish. But the highlight of the center is its observation deck, from which visitors can peer over the side of the massive dish. There’s also a great gift shop that sells all kinds of great educational books, models, and toys. It’s a good source for maps of the island too.