Heinz-Harald Frentzen's lap of Monaco.

This weekend's Monaco Grand Prix, the jewel in Formula One's crown despite complaints about the track and its pit-lane, will feature a slightly remodelled circuit layout, giving the drivers something else to think about as they emerge for first practice on Thursday morning.

With concrete walls and steel barriers ever waiting to claim the unwary, the circuit remains the toughest on the schedule, and Monaco veteran Heinz-Harald Frentzen knows just how he is going to tackle the race.

''Ste Devote, the first corner at Monaco, is like a funnel,'' he said, beginning a review of the lap, ''It gets narrower, especially in the race when there are cars all around you. And, in past years, the entry has been bumpy, though some resurfacing there may have changed that. I'll be curious to see what effect it has had.

''The first person to slide off-line there in the race gets on to the used rubber, and then they go into the wall. The [marshals] clean the track after each practice session but, in the race, you still have to be really careful here. You have to be very precise every lap - you have to be on exactly the same line, and any slight lapse in concentration can catch you out. There are a couple of corners at Monaco where this is valid, and you need to maintain your rhythm and procedure.

''The climb up the hill to Massenet is relatively undramatic because, even though the road winds, you just take the one standard line through the curves until you come to the left-hander at Massenet. You have to commit to the apex before you can see it, because it is obscured by the barrier. You have to feel your way in, rather than see your way in. You have to find your way with no visual confirmation, and again you need to be on exactly the same line every lap.

''There is also only one line at Casino Square, the right-hander which follows. You flirt with the barrier here on the exit, but there is a big bump in the road and you have a choice of keeping to the left and going over it, or pulling to the right to miss it and maintain downforce. Personally, I like to go halfway! At Casino Square, the balance of the car changes as the race progresses. You begin with understeer, but the car ends up oversteering before you change tyres. You continuously have to adapt, lap by lap.

''Mirabeau is next, a tight downhill right-hander that leads into an important sequence of corners. The track is bumpy here and you are braking hard while carrying speed downhill, so there isn't a lot of grip. And, as you turn in, the road drops away and the inside wheel is in the air, so the grip is reduced further. There's a lot of camber change, too. The combination is quite exciting.

''You accelerate quickly down to the Grand Hotel Hairpin, a left-hander that became famous under the name of Loews. This is quite tricky too, because it's not an ordinary hairpin. If you get good traction out of Mirabeau, you can hit 145kph before braking hard but, if traction isn't so good, you might only hit 135, so you need to be careful how you approach the corner. If the momentum isn't what you expected, and the car isn't sliding so much as you anticipated, it's easy to clip the left-hand kerb and to throw the car in the air and lose grip and momentum. Braking and turn-in here is thus critical, and it's easy to lose a couple of tenths.

''The unnamed right-hander that follows is another one where you need to be careful about choice of line. How well you get through here is also a product of your exit from the Grand Hotel Hairpin. Portier is next, the 90 degree right-hander leading into the tunnel. You brake a little and then pick up the throttle early. The mistake you can make here is to turn in too early, in which case you can catch the right front wheel on the inside barrier, but you need to be close to it to make the apex.

''You are flat on the throttle all the way through the tunnel, but you can't see the clean line in the dark section so it's difficult to see if any oil has been dropped. Going from the dark into sunlight isn't so bad, though. The run down to the chicane is the fastest part of the course; you hit around 280 as you get to the top of the hill, which is where you really need to begin braking if you are going to avoid going down the escape road or running over the chicane. This requires the hardest braking anywhere on the circuit, and you take the chicane in first or second gear before accelerating up to fifth gear to Tabac. The entry here used to be quite bumpy, but it's been resurfaced and is now okay.

''I really like the combination of Tabac's left-hander and then the left/right flick that follows at the Swimming Pool. It's really challenging, and there are a lot of possibilities to get it wrong. There are a lot of hidden lines, and it's also difficult to judge. It's another of those corners where the apex is hidden, and the barrier doesn't follow a perfect radius, so you can get caught out by kinks in it if you try to follow it too slavishly. Not counting the tunnel, which isn't really a corner, the left/right kink is the fastest corner on the track.

''The circuit has been changed after the Swimming Pool this year, with a new entry to Rascasse. This has taken away two crucial points where you could have an accident. It used to be very difficult if you over-braked there, as you could end up in the wall. Now there is a run-off so you have some margin for error. Now, if you make a mistake, you lose the lap, but not necessarily the car, although you could end up going for a drink at 'Stars & Bars'!

''Now you have a straight run to Rascasse, but you still need to be careful under braking, of course, because you are carrying more speed. You've lost the risk in two corners, but you must still be aware of a risk in one. I'm going to be interested to see what it's like there now.

''The final corner is called Noghes, and it's another tricky one. It's easy to slide the car there and tap the barrier. It's another one where you can't see the apex until you are already on it. You have to turn in while accelerating the car, and there is an odd camber change. If you are just a couple of centimetres off line, it's easy to hit the right front wheel on the barrier, and if you oversteer on the exit, to hit the left rear. The pit straight isn't actually a straight, but they have done a lot of work on it this year and a lot of the bumps have been removed. That should make the start a little easier, too.''