Most visitors to Oxford want to visit the university's many historic colleges, with their beautiful grounds and stunning architecture.

One of the great strengths of Oxford is that each college is so different, and they all have their individual points of interest. It is easy to avoid being like the tourist who asked for directions to "the campus of Oxford University", but many visitors do fall into the subtler trap of forgetting that colleges are living, breathing institutions devoted to learning, and not designed just for tourists.

For many students and tutors, college is where they live as well as work. The Easter and summer terms may be popular times for visitors to look round the college, but don't forget that some students are sitting their final or first-year exams during these times. Do not add to their stress by exploring parts of colleges which are not open to the public.

All Souls was founded in 1438, and the front quadrangle (also known as the old quadrangle) is virtually unchanged since then, although there are battlements which were added in the early 16th century.

The north quadrangle (also known as the great quadrangle) is mainly Gothic style, with twin towers.

It is open to the public 2pm to 4pm, Monday to Friday. Free admission.

Tel: 01865 279379, website: www.all-souls.ox.ac.uk

Balliol College dates from the 13th century and can be found on Broad Street in the town centre. Look out for the scorch marks on the wooden doors between the inner and outer quadrangles. They are a grisly reminder of when the Protestant martyrs Bishops Latimer and Ridley and Archbishop Cranmer were burnt at the stake for their faith in the 1550s.

Usually open to the public between 1pm and 5pm (but call before visiting to confirm). Adults £1, children free.

Tel: 01865 277777, website: www.balliol.ox.ac.uk

Christ Church is on St Aldate's and is one of Oxford's most famous colleges. The college chapel is Christ Church Cathedral, which is well worth a visit.

From Monday to Friday, the cathedral opens to the public at 10am until 11.45am, and again from 2.15pm to 4.30pm.

On Saturdays, it usually closes at 4.30pm. The dining hall normally opens by 10.30am on weekdays, then closes at 11.45am before reopening at 2.15pm, and finally closing at 4.30pm.

On Sundays, the cathedral opens to the public between 1pm and 4.30pm during term-time (it is used for services in the mornings). The dining hall is closed on Saturday and Sunday mornings in term-time, opening between 2.30pm and 4.30pm.

Opening hours vary and can change at very short notice because Christ Church is a busy institution. It pays to ring ahead and check before paying a visit. Speak to the head custodian on 01865 276492.

Price of admission is £4.70 for adults and £3.70 for children, students and OAPs. You can also buy a family ticket for £9.40.

Website: www.chch.ox.ac.uk

Keble is on Parks Road, near the University Parks. It is well known for its multi-coloured design, created by William Butterfield in the 19th century. It is also known for its ultra-modern college bar, nicknamed the spaceship' by students.

Open to the public throughout the day, although this is subject to change. Admission is free.

Tel: 01865 272727, website: www.keble.ox.ac.uk

The Queen's College has a front quad which has been called the grandest piece of classical architecture in Oxford. The college is on the High Street and many buses stop right outside, which makes it a very convenient college to reach.

However, the college is only open to visitors taking a pre-arranged tour. To book call Oxford's Tourist Information Centre on 01865 726871.

Website: www.queens.ox.ac.uk

Hertford's best-known feature is the Bridge of Sighs, which connects one part of the college to another. It is named after, and built in imitation of, Venice's own Ponte dei Sospiri.

Although it does not resemble its Venetian namesake very closely, it is one of Oxford's best-known landmarks.

Hertford is also famous for reportedly being the college about which Evelyn Waugh wrote Brideshead Revisited.

It is normally open from 10am to noon and then from 2pm until dusk. However, this may change in some weeks, particularly during the exams in Trinity term (after Easter) so it is a good idea to ring and check. Admission is free.

Tel: 01865 279400, website: www.hertford.ox.ac.uk

Magdalen was founded in 1458 by the Bishop of Winchester, and can be found on the High Street.

The core of the college was built in the late 15th and early 16th century, although the building, which is now the college bar, was part of an old hospital dating from the late 13th or early 14th century.

Magdalen College Chapel is one of the most active in the university, with 15 services a week during full term.

It is open to the public from 1pm until dusk October 1 until March 31, 1pm until 6pm from April 1 to June 30, and noon to 6pm from July 1 until September 30.

Admission is £3 for adults, £2 for students and OAPs.

No charge for residents of Oxford.

Tel: 01865 276000, website: www.magd.ox.ac.uk