Jutting south from Mount Fuji into the Pacific, the Izu Peninsula has something of a holiday air about it. The warm Kuroshio current flowing northward lends the peninsula a mild climate, and its position close to the suture lines of shifting tectonic plates means that rugged Izu has no lack of geothermal springs.

At the northeastern end of the peninsula is Atami — a hot-spring resort and dirty-weekend spot par excellence for those in the capital. Moving down the peninsula from Atami, you pass a string of spas, clutches of small museums and other diversions, one is which is called the Banana and Alligator Park. Then you reach, near the southern tip, the port of Shimoda.

The first impression of Shimoda today is that of a pleasant, sleepy little town — an impression that doesn’t fit so readily with the fact that a century and a half ago it was the focal point of Japan-U.S. relations. Adroitly using gunboat diplomacy, Commodore Matthew Perry of the U.S. Navy forced the signing of the Kanagawa Treaty in March 1854, ending the national seclusion that Japan had imposed upon itself for more than two centuries.

Perry had demanded that ports be opened to American vessels, and Shimoda was one of the two selected. After signing that treaty, Perry sailed down the Izu Peninsula to see Shimoda, which had been appointed as the site of the first U.S. consulate in Japan, and there he signed an additional treaty guaranteeing freedom of movement for Americans in the town.

As might be imagined, intruder Perry was not a popular figure in Japan at the time. When he first arrived in the country, the Japanese begged him to go away again. Contemporary portraits of him, as displayed in Ryosenji Temple, where Perry signed the Shimoda Treaty, were at pains to convey the impression that he was not so much human as a devil, and a very ugly one at that. Impressions, of course, change with time.

Now, Shimoda — which holds a Black Ships Festival every May, marking the arrival of the first Americans — has coopted Perry into its own public image, and looks on the commodore with much fonder eyes.

The modern image of the man, as portrayed in a bust atop the Perry monument beside the harbor, displays a statsemanlike person of great dignity and intelligence. No longer a demon.

Of all the links with Perry, the most conspicuous in Shimoda is the Susquehanna, modeled on one of the seven ships that brought Perry and his fellow 1,264 Americans to the port. The Susquehanna is used to ferry tourists on cruises around the harbor, and the vessel has a jolly leisure-boat vibe about it, with tourists trooping about and kids shouting. So it is difficult, then, viewing this craft, to get any notion of the tremendous fear that Perry’s ships inspired among the Japanese. Weighing 127 tons, today’s Susquehanna is just one-quarter the size of the original ship of the same name, yet the largest Japanese vessels in Perry’s day weighed only 100 tons. The Japanese had never seen such enormous ships, and Perry’s bristled with firepower. To ensure there was no doubt about his message, Perry fired a thundering 17-gun salute before setting off from his ship to begin negotiations on the Shimoda Treaty.

Connecting the harbor with Ryosenji is the quiet thoroughfare known as Perry Road, which skirts past some of Shimoda’s older buildings. Though the justification for the name of this street rests, according to the pamphlet published by the Shimoda tourist office, on the limp claim that “Perry is said to have once walked” along it, a pleasant old character does hang over the Perry Road district. Plants adorn window boxes; willows droop lazily into the waterway; shops sell antiques and curios; streets are lit by old-fashioned lamps. In evidence here are buildings with namako-kabe, a distinctive architectural feature of southern Izu. Though namako-kabe translates unappealingly as “sea-slug walls,” these walls are in fact rather handsome affairs and consist of dark tiles arranged in diamond patterns, with white plaster used to seal the joints. The rounded lines of the plaster are thought to resemble sea slugs and hence supply the name.

If Perry Road is the best place for a stroll in Shimoda, the finest view is to be had from Mount Nesugata, which is reached by cable car from the town. From the top of this hill, Shimoda’s superb natural harbor, which would certainly have delighted Perry, stretches grandly into view. At the summit of Nesugata stands the Renjo Photo Memorial Hall, which traces the history of photography back to the days when a camera was not something that came with the cell phone but was a strapping contraption the size of a small trunk. And if you and your beloved wish to have a photo of yourselves standing in front of a faux stained-glass window — he dressed in braided uniform looking like a 19th-century admiral of the fleet, she in a blue ballroom dress looking like a frumpy extra in a palace scene from “Doctor Zhivago” — you really have come to the right spot.

Shimoda’s time in the limelight was brief. The treaties of 1854 contained no provisions for commerce. It was not until the signing of additional treaties, four years later, that several Japanese cities, including Edo (now Tokyo) and Osaka, were opened to international trade. These treaties also provided for diplomatic exchanges, and with them Shimoda’s importance slid into rapid decline.

And so Shimoda has remained as the place we see today, which is an attractive quiet port of around 30,000 people nestled among hills and built on a winding river that feeds into the long sleeve of its harbor. Sitting upon one of those hills is the town’s pint-size castle, which adds an additional historical dimension to the town. Shimoda may no longer have the importance it once did, but, as is often the case, some of the pleasanter places are those that history has edged neatly onto the sidelines.