knowledge - Gladys visits a campus

_{This puzzle is part 9 of Gladys' journey across the globe. Each part can be solved independently. Nevertheless, if you are new to the series, feel free to start at the beginning: Introducing Gladys.}

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Dear Puzzling,

Today I wanted to see a local educational institution. It may not be the most exciting tourist destination, but I enjoyed it a lot. Museums and churches are great, of course, but it's nice to get to talk with young people for a change.

Wish you were here!
Love, Gladys.

P.S. One rule for today's puzzle: A number is worth two letters!

Across
2. Destination of an emigrant trail
3. Wanted to tear down a wall

4. Program used in AA
6. Green vegetable
7. 25%
8. Historical military ruler
9. Segregated urban area
11. Musician behind Live Aid
13. President's daughter
15. Waiter or computer
16. Object with magical powers
17. James Bond

18. Burnt colour
19. Existing being

Down
1. Used for dating by archaeologists
3. Greatly enjoy
5. With sign, light or fighter
6. Sydney Harbour or George Washington
10. Tropical bird
12. Median lethal dose
14. Japanese sword

15. David Fincher thriller

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_{Gladys will return in "The hearts of gold".}

Answer

Gladys is at

Oran 1 University in Oran, Algeria

The gimmick with this crossword is that

every square has to be occupied by either two letters or one numeral. For example, 4A is 12 STEP, so you put the 1 and 2 in the first and second squares, then ST and EP in the last two.

Completed gridI:

(Credit to @Rubio for this much better and cleaner grid! If you want to see the original (terrible) handwritten grid, click here.)