The Fort Pitt Block House, the oldest structure in the city, reopens tomorrow in the same spot it has held since 1764, yet finds itself in new environs yet again.

Through the centuries, it has gone from an 18th-century outpost in the wilderness to a 19th-century home and candy store to something of a historical afterthought in a late 20th-century park more famed for concerts, regattas and arts festivals with greasy food.

Its historic importance may be clearer than ever now that the multimillion-dollar makeover of Point State Park has covered the recreated bastions of Fort Pitt. That gives the park a grand sweeping front lawn uninterrupted by ditches.

Kelly Linn, the Block House curator, did not oppose that change.

"I'm older than most of the bricks that were in that wall," Ms. Linn, 46, said of those departed bastions.

Besides, the new alignment, which will allow more to happen on the Downtown side of the underpass, "spares this building the indignity of being the Porta-John site."

The Block House is the real deal, the last vestige of Britain's short-lived American Empire. It was built a year after Pontiac's War began, a fearsome frontier uprising named for an Ottawa chief who helped organize the Indian tribes of the Great Lakes; it would leave more than 2,000 settlers killed or captured.

In the summer of 1763, more than 500 colonists crowded inside Fort Pitt, including more than 200 women and children. That summer is notorious for the fort's Swiss-born commander, Capt. Simeon Ecuyer, ending a parley with Delaware leaders with gifts of blankets -- blankets freshly infested with smallpox. This early attempt at biological warfare evidently failed and the siege continued, but it's indicative of the ruthlessness of both sides in the frontier wars.

That's all a very long way from a noontime stroll in the park, or a summer jazz concert, which is how most people know this land. But that only makes a walk into a little, five-sided brick building more striking.

"This building was built for the enemy that never came," Ms. Linn said.

All the bricks date from the 1760s. The rafters are original. So are the gun loop timbers, from which soldiers "could extend the field of musket fire beyond the walls of Fort Pitt [90 feet to the east] and also create a protective field of crossfire between the bastions of the fort," according the brochure.

No shots should have been fired from the house, but a musket ball found in one of the timbers indicates at least one British Colonial's gun went off. Ms. Linn showed me rough notches in the lower rafters, about where soldiers would have been climbing to the second level via a ladder, and she says they came from soldiers' musket barrels repeatedly hitting there on the way up.

The British abandoned Fort Pitt in 1772 as pre-revolutionary tensions with colonists grew, and the fort was dismantled in the early 1800s. The block house survived as a residence for more than 100 years, and was broken into apartments by the 1830s, with the residents playing off its history to give tours.

In 1894, a woman named Sarah Powers, better known as "Aunt Sibby," was living there. She sold hard candy and cookies to help make her $5 rent. Ms. Linn built a small window exhibit to show what she might have had, "five dried ginger snaps and oranges perched on tea cups," according to the contemporary newspaper accounts.

That was the year the Fort Pitt Society of the Daughters of the American Revolution was given the place by Mary Schenley. The DAR later took on Henry Clay Frick and the Pennsylvania Railroad to keep this building in place when it was threatened by eminent domain, beating the industrialists in court at a time when women didn't even have the right to vote.

For Ms. Linn, an archaeologist who grew up in West Mifflin, this is her dream job. She's running the oldest continuously operating museum in the city, "beating the Carnegie by a couple of months."

The Fort Pitt Block House is open Wednesday through Sunday, 10 a.m. to 5 p.m., year round, and is free to the public. It has a phone number -- 412-471-1764 -- but is refreshingly free of a Web site.