The phrase "a town which is" is correct and usable in written English.
It can be used to provide additional information or description about a town in a sentence.
Example: "I visited a town which is known for its beautiful architecture and rich history."
Alternatives: "a town that is" or "a town where".
"It's a town which is under rocket attacks.
He stops in a town which is probably in Tennessee, and accidentally locks his keys in the car.
"What happened in Adado is very serious, especially to attack a town which is relatively peaceful," President Sheik Sharif Sheik Ahmed, the leader of Somalia's beleaguered transitional government, said after Friday Prayer.
He stops in a town which is probably in Tennessee, and… The narrator, a professor who lives with his wife and children on the coast of New England, is giving a lecture series at a university… The writer tells about the estate near Siena, in Italy, where he lived with his family.
By 2011, when the last of the coal ash had been shifted from Harriman, a town which is 90% white, to a landfill on the outskirts of Uniontown, which is 90% black, it had formed the highest peak in Perry County.
And now I'd come to Toksan, a town which isn't the prettiest, and it's pouring so hard I'm sheltering under a shop's awning, and that tent in my backpack doesn't seem so useful now.
Hvorostovsky's musical education took place in Krasnoyarsk, a town which was closed to foreigners until the late 1980s.
Carneiro says she fell in love with football while in Brazil during the 1998 World Cup: "Brazil was playing Mexico and we stopped at a town which was a popular honeymoon tourist destination for Brazilians.
The Peruvian authorities have announced a state of emergency in a town which was hit by an avalanche of mud and rocks on Monday.
There is an equestrian statue in Gloucester, England, a town which was founded in his honour.
The images from the satellite IRS 1A shows Thiruthuraipoondi was a coastal town (which is an inland in modern times) and the sea has regressed up to Vedaranyam in modern times.
