Mostly edged by Victorian red-brick buildings, the mazy streets of Boston's cramped and compact centre, on the east side of the Witham, radiate out from the Market Place , a dishevelled square of irregular shape. Just to the west looms the massive bulk of St Botolph (May-Sept daily 8.30am-4.30pm; Oct-April Mon-Sat 8.30am-4.30pm, Sun 8.30am-12.30pm; free), whose exterior masonry is embellished by the high-pointed windows of the Decorated style. Most of the structure dates from the fourteenth century, but the huge and distinctive tower , whose lack of a spire earned the church the nickname the "Boston Stump", is of later construction. The octagonal lantern is later still, added in the sixteenth century and graced by flying buttresses and pointy pinnacles. A tortuous 365-step spiral staircase (closed on Sun) leads to a balcony near the top, from where the panoramic views over Boston and the fens amply repay both the price of the ticket (A?2) and the effort of the climb. Down below, St Botolph's light and airy nave is an exercise in the Perpendicular, all soaring columns and high windows. The sheer purity of design is stunning, its virtuosity heightened by the narrowness of the annexe-like chancel and the elegance of the Decorated arch that partly screens it from view.

The church's most famous vicar was John Cotton (1584-1652), who helped stir the Puritan stew during his twenty-year tenure, encouraging a stream of Lincolnshire dissidents to head off to the colonies of New England to found their "New Jerusalem". Cotton emigrated himself in 1633 and soon became the leading light among the Puritans of Boston, Massachusetts. The Cotton connection was finally commemorated here in the Stump by the creation of the Cotton Chapel , at the west end of the nave, in 1857.

Boston had been alive to religious dissent before Cotton arrived and, in 1607, several of the Pilgrim Fathers were incarcerated here after their failed attempt to escape religious persecution by slipping across to Holland. They were imprisoned for thirty days in the old Guildhall (Tues-Sat 10am-5pm; A?1.25, free on Thurs), on South Street - a brief walk south along the river from St Botolph. A creaky affair, the Guildhall spreads over three levels and incorporates an antique Council Chamber, the court where the Pilgrim Fathers were tried and sentenced, as well as the cells where they were locked up. There's a fascinating hotchpotch of local bygones dotted around - including some spectacularly ferocious anti-poacher traps and a small display on locally born John Fox (1516-87), whose Book of Martyrs whipped up an anti-Catholic storm.