The busiest of Maastricht's many squares is Markt , at its most crowded during the Wednesday and Friday morning market . At the centre of the square, the 1664 Stadhuis (Mon-Fri 8.30am-12.30pm & 2-5.30pm; free), a typical slice of mid-seventeenth-century Dutch civic grandeur, was designed by Pieter Post. Just west, Vrijthof is a grander open space flanked by a line of cafA© terraces on one side and on the other by St Servaaskerk (daily 10am-5pm; a?¬1.80). Only the crypt remains of the original tenth-century church; the rest is mostly of medieval or later construction. On the northern side of the church, the fifteenth-century Gothic cloister leads into the treasury, which holds a large collection of liturgical accessories, including a bust reliquary of St Servaas, which is carried through the town in Easter processions. The second most prominent building on the square, next door, is Maastricht's main Protestant church, the fourteenth-century St Janskerk (Easter-Oct Mon-Sat 11am-4pm; free), the baptistry of the church of St Servaas when it was a cathedral and nowadays competing for attention with its high fifteenth-century Gothic tower (a?¬1.10 donation). Inside are some medieval murals, but otherwise climbing the tower is the church's main appeal. Maastricht's other main church, the Onze Lieve Vrouwe Basiliek , is a short walk south of Vrijthof, down Bredestraat, in a small shady square crammed with cafA© tables. Founded around 1000, its dark and eerily devotional interior, with a gorgeous galleried choir, is fronted by an unusual fortified west facade. Off the north aisle, the treasury (Easter to midSept Mon-Sat 11am-5pm, Sun 1-5pm; a?¬1.60) holds the usual array of ecclesiastical oddments, most notably the tunic of St Lambert, a bishop of Maastricht who was murdered at LiA?ge in 705.

Around the corner from the square, on Plankstraat, the Museumkelder Derlon (Sun noon-4pm; free), in the basement of the hotel of the same name, contains a few remnants of Roman Maastricht - the remains of a temple to Jupiter, a well and several layers of pavement, discovered during the building of the present hotel in the mid-1980s. On the other side of the square lies another of Maastricht's most appealing quarters, narrow streets winding out to the fast-flowing River Jeker, which weaves around the various houses and ancient mills and the best surviving part of the city walls, the Helpoort of 1229. Continuing south, the Casemates in the Waldeck Park (guided tours: July & Aug daily 12.30pm & 2pm; rest of year Sun 2pm; a?¬2.70) are further evidence of Maastricht's once impressive fortifications, a system of galleries created through mining between 1575 and 1825 that were used in times of siege for surprise attacks on the enemy. Fifteen minutes' walk further south are more dank passageways, hollowed out of the soft sandstone or marl that makes up the flat-topped, 110m hill of St Pietersberg . Of two cave systems, the Zonneberg is probably the better, situated on the far side of the hill at Casino Slavante (guided tours: July & Aug daily 2.15pm; a?¬2.70). There's some evidence of wartime occupation, plus what everyone claims is Napoleon's signature on a graffiti-ridden wall.