Sewer: Examine the machinery.
First room: If it's broke, fix it!
Second room: Reading is fundamental.
Sewer: You are in a sewer; ahead of you is a gate with a ladder behind it. To open the gate, click over to the crank. Pick up the little handle and place it in the hole on the top of the crank. Then click to turn the crank until the boat rises; continue until it stops. The gate should now be open; go up the ladder and turn the door handle.
Useless things to play with: the brazier to the left of the crank (pick up the coal on the floor, put it in the brazier, and watch the flame flare up); the skeleton on the wall (running the cursor over the missing thigh bone area produces a "click" -- but remember this for the endgame).
Cornelius's Office: At the model city, click on the fallen buildings to pick them up; a scroll pops up; read it, and click on the picture to run the little mini-video that shows you where Cornelius's desk is. Picking up the little buildings also opens the door to the next room, where Cornelius's desk is. Go to the desk, read all the scrolls and the note, click on the box to open it (you can't open the box until after you've clicked on the note), and get the crank. It will fly over to the Navitor. You might also want to play with the four machines a bit; each one is associated with a season. Ver=Spring; Aestas=Summer; Autumnus =Autumn; Hiems=Winter. Notice that there are also doors marked "Ver" and "Autumnus". This will give you an idea of what to do and where to go when you need to restart the Navitor after its seasonal breakdowns in March, June, September, and November.
Start the Navitor by pulling the crank to the right. Here's how it works:
Time. The crank can be manipulated to slow down or speed up the passage of time; slower to the left, faster to the right. All the way to the left brings you back to Cornelius's study; pull to the right to restart. All the way to the right will go extra fast if you grab the pointer with the mouse, move it to the right, then release the mouse button without moving the hand away from the pointer. This is very useful for advancing to the next date that something will be open if you don't feel like wandering around waiting for time to pass automatically. Keep it at a slow-to-moderate pace at the beginning, until you've familiarized yourself with the Forum and done everything you need to do the first month. You cannot go backward in time, unless you reload a saved game (see below).
The center of the timebar indicates today's date in ancient Roman reckoning: "a.d." stands for "ante diem," or days before; "Kal." stands for Kalends, the first day of the month; "Non." stands for Nones, the 5th or 7th day of the month; and "Id." stands for Ides, the 13th or 15th day of the month. "Pridie" stands for the day before, i.e., the "eve" of the Kalends, Nones, or Ides of the month. Thus, for example, "a.d. XII Kal. Aug." is 12 days before the 1st of August -- in other words, you're in July, but past the Ides (or middle) of July. Nearly all of the places you have to visit to solve the puzzles will have specific opening dates (e.g., the Regia sign says "Apertus XIV Kal. Nov.", which is in October). Some dates will be indicated in the scrolls or Acta. You cannot get inside the place to solve the puzzle until on or after the specified date.
Calendar: The scroll just above the timebar brings up a visual clue to where you'll need to solve that month's puzzle. There is one major puzzle each month (in addition to many minor ones). Press the button to the right to go forward and get a preview; the one to the left moves backward. You should solve each month's puzzle, if at all possible, before moving on to the next month, otherwise you will be hampered at the end of the game. Saving your position on the Nones of each month will always give you a chance of retrying.
Info. The nameplates contain the characters' notebooks, containing useful historical information about all aspects of ancient Rome, as well as clues to some of the puzzles you'll encounter as you go along. To get a table of contents, click on the initial on the bottom left of the notebook scroll. To move forward in the scrolls, click on the right; backward, to the left. The "Exitus" button exits the notebook. When a name is lit, click to read the notebook entry; it may contain clues. You can read the notebooks any time, even when the name isn't lit.
Storage: Most of the non-scroll items you pick up (i.e., those not to be used immediately) will be stored in one of the two cabinets at the bottom left and right of the Navitor. The doors move down to open and up to close.
Maps: The storage doors, when closed, have two maps. The one on the left is architectural, and allows you to click on individual buildings to see their layout. The one on the right is of the city itself. The places you visit are marked with circles; a flashing circle is where you're at now. You can hyperjump from one place to another by clicking on a circle near where you want to be. The names of the places are indicated at the bottom of the map as your cursor moves over them. Look for the turned-down edges indicating that you can turn the page to see more maps. "Exitus" exits.
Compass: Bottom right. For use in conjunction with the city map. It generally shows you which way you're facing, but it's often unreliable (as Cornelius warns). The city map is a much more trustworthy means of getting around.
Acta Diurna: Bottom left. Dated official mouthpiece of the Emperor; flashes when there's a new one. Can contain clues and indications as to when an important festival will be or when and where a crime you need to "investigate" was committed. Can be read anytime, even when not flashing, and you can go backward and forward (click "Retro" for backward; click on the right to go forward) but you cannot go into the future. Some Acta go beyond one page -- look for a "Cont." button. "Exitus" to exit.
Scrolls: Each character's dated scrolls are stored on the five-slot shelf below the viewer. (See January for where to find all five.) A new scroll is indicated when it unfurls; click on it to read it. You can read scrolls even when they're furled; click, and the most recent one appears. Like the Acta, you can go backward or forward (look for the furled edges), but not beyond the date you're at. Scrolls contain textual and visual clues to minor and major puzzles, as well as giving an idea of each character's history and personality, and his or her possible motives for being the Calamitus.